diff --git a/code/BatchActions/CMSBatchAction_Restore.php b/code/BatchActions/CMSBatchAction_Restore.php
index 276b4a837b..340d9db05a 100644
--- a/code/BatchActions/CMSBatchAction_Restore.php
+++ b/code/BatchActions/CMSBatchAction_Restore.php
@@ -57,6 +57,6 @@ public function applicablePages($ids)
 
         // Get pages that exist in stage and remove them from the restore-able set
         $stageIDs = Versioned::get_by_stage($this->managedClass, Versioned::DRAFT)->column('ID');
-        return array_values(array_diff($ids, $stageIDs));
+        return array_values(array_diff($ids ?? [], $stageIDs));
     }
 }
diff --git a/code/Controllers/CMSMain.php b/code/Controllers/CMSMain.php
index 8b75e3a91e..f88d01e05d 100644
--- a/code/Controllers/CMSMain.php
+++ b/code/Controllers/CMSMain.php
@@ -184,7 +184,7 @@ protected function init()
     {
         // set reading lang
         if (SiteTree::has_extension('Translatable') && !$this->getRequest()->isAjax()) {
-            Translatable::choose_site_locale(array_keys(Translatable::get_existing_content_languages(SiteTree::class)));
+            Translatable::choose_site_locale(array_keys(Translatable::get_existing_content_languages(SiteTree::class) ?? []));
         }
 
         parent::init();
@@ -454,7 +454,7 @@ public function LinkWithSearch($link)
         ];
         $link = Controller::join_links(
             $link,
-            array_filter(array_values($params)) ? '?' . http_build_query($params) : null
+            array_filter(array_values($params ?? [])) ? '?' . http_build_query($params) : null
         );
         $this->extend('updateLinkWithSearch', $link);
         return $link;
@@ -470,7 +470,7 @@ public function LinkPageAdd($extra = null, $placeholders = null)
         }
 
         if ($placeholders) {
-            $link .= (strpos($link, '?') === false ? "?$placeholders" : "&$placeholders");
+            $link .= (strpos($link ?? '', '?') === false ? "?$placeholders" : "&$placeholders");
         }
 
         return $link;
@@ -627,7 +627,7 @@ public function getTreeNodeClasses(SiteTree $node)
         // Get status flag classes
         $flags = $node->getStatusFlags();
         if ($flags) {
-            $statuses = array_keys($flags);
+            $statuses = array_keys($flags ?? []);
             foreach ($statuses as $s) {
                 $classes .= ' status-' . $s;
             }
@@ -642,7 +642,7 @@ public function getTreeNodeClasses(SiteTree $node)
             $classes .= ' ' . $filterClasses;
         }
 
-        return trim($classes);
+        return trim($classes ?? '');
     }
 
     /**
@@ -664,8 +664,8 @@ public function getsubtree($request)
         );
 
         // Trim off the outer tag
-        $html = preg_replace('/^[\s\t\r\n]*<ul[^>]*>/', '', $html);
-        $html = preg_replace('/<\/ul[^>]*>[\s\t\r\n]*$/', '', $html);
+        $html = preg_replace('/^[\s\t\r\n]*<ul[^>]*>/', '', $html ?? '');
+        $html = preg_replace('/<\/ul[^>]*>[\s\t\r\n]*$/', '', $html ?? '');
 
         return $html;
     }
@@ -682,7 +682,7 @@ public function getsubtree($request)
     public function updatetreenodes($request)
     {
         $data = [];
-        $ids = explode(',', $request->getVar('ids'));
+        $ids = explode(',', $request->getVar('ids') ?? '');
         foreach ($ids as $id) {
             if ($id === "") {
                 continue; // $id may be a blank string, which is invalid and should be skipped over
@@ -824,7 +824,7 @@ public function savetreenode($request)
 
             $this->getResponse()->addHeader(
                 'X-Status',
-                rawurlencode(_t(__CLASS__.'.REORGANISATIONSUCCESSFUL', 'Reorganised the site tree successfully.'))
+                rawurlencode(_t(__CLASS__.'.REORGANISATIONSUCCESSFUL', 'Reorganised the site tree successfully.') ?? '')
             );
         }
 
@@ -852,7 +852,7 @@ public function savetreenode($request)
 
             $this->getResponse()->addHeader(
                 'X-Status',
-                rawurlencode(_t(__CLASS__.'.REORGANISATIONSUCCESSFUL', 'Reorganised the site tree successfully.'))
+                rawurlencode(_t(__CLASS__.'.REORGANISATIONSUCCESSFUL', 'Reorganised the site tree successfully.') ?? '')
             );
         }
 
@@ -923,7 +923,7 @@ public function getSearchFieldSchema()
 
         $searchParams = array_combine(array_map(function ($key) {
             return 'Search__' . $key;
-        }, array_keys($searchParams)), $searchParams);
+        }, array_keys($searchParams ?? [])), $searchParams ?? []);
 
         $schema = [
             'formSchemaUrl' => $schemaUrl,
@@ -1082,7 +1082,7 @@ public function Breadcrumbs($unlinked = false)
 
         // Add all ancestors
         $ancestors = $record->getAncestors();
-        $ancestors = new ArrayList(array_reverse($ancestors->toArray()));
+        $ancestors = new ArrayList(array_reverse($ancestors->toArray() ?? []));
         $ancestors->push($record);
         /** @var SiteTree $ancestor */
         foreach ($ancestors as $ancestor) {
@@ -1144,7 +1144,7 @@ public function SiteTreeHints()
             // Check if can be created at the root
             $needsPerm = $obj->config()->get('need_permission');
             if (!$obj->config()->get('can_be_root')
-                || (!array_key_exists($class, $canCreate) || !$canCreate[$class])
+                || (!array_key_exists($class, $canCreate ?? []) || !$canCreate[$class])
                 || ($needsPerm && !$this->can($needsPerm))
             ) {
                 $def['Root']['disallowedChildren'][] = $class;
@@ -1226,7 +1226,7 @@ public function getRecord($id, $versionID = null)
         if ($id instanceof $treeClass) {
             return $id;
         }
-        if (substr($id, 0, 3) == 'new') {
+        if (substr($id ?? '', 0, 3) == 'new') {
             return $this->getNewItem($id);
         }
         if (!is_numeric($id)) {
@@ -1459,18 +1459,18 @@ protected function getArchiveWarningMessage($record)
 
         // Count number of affected change set
         $affectedChangeSetCount = 0;
-        if (count($inChangeSetIDs) > 0) {
+        if (count($inChangeSetIDs ?? []) > 0) {
             $affectedChangeSetCount = ChangeSet::get()
                 ->filter(['ID' => $inChangeSetIDs, 'State' => ChangeSet::STATE_OPEN])
                 ->count();
         }
 
         $numCampaigns = ChangeSet::singleton()->i18n_pluralise($affectedChangeSetCount);
-        $numCampaigns = mb_strtolower($numCampaigns);
+        $numCampaigns = mb_strtolower($numCampaigns ?? '');
 
-        if (count($descendants) > 0 && $affectedChangeSetCount > 0) {
+        if (count($descendants ?? []) > 0 && $affectedChangeSetCount > 0) {
             $archiveWarningMsg = _t('SilverStripe\\CMS\\Controllers\\CMSMain.ArchiveWarningWithChildrenAndCampaigns', 'Warning: This page and all of its child pages will be unpublished and automatically removed from their associated {NumCampaigns} before being sent to the archive.\n\nAre you sure you want to proceed?', [ 'NumCampaigns' => $numCampaigns ]);
-        } elseif (count($descendants) > 0) {
+        } elseif (count($descendants ?? []) > 0) {
             $archiveWarningMsg = $defaultMessage;
         } elseif ($affectedChangeSetCount > 0) {
             $archiveWarningMsg = _t('SilverStripe\\CMS\\Controllers\\CMSMain.ArchiveWarningWithCampaigns', 'Warning: This page will be unpublished and automatically removed from their associated {NumCampaigns} before being sent to the archive.\n\nAre you sure you want to proceed?', [ 'NumCampaigns' => $numCampaigns ]);
@@ -1693,9 +1693,9 @@ public function ListViewForm()
                 );
                 $breadcrumbs = $item->Breadcrumbs(20, true, false, true, '/');
                 // Remove item's tile
-                $breadcrumbs = preg_replace('/[^\/]+$/', '', trim($breadcrumbs));
+                $breadcrumbs = preg_replace('/[^\/]+$/', '', trim($breadcrumbs ?? ''));
                 // Trim spaces around delimiters
-                $breadcrumbs = preg_replace('/\s?\/\s?/', '/', trim($breadcrumbs));
+                $breadcrumbs = preg_replace('/\s?\/\s?/', '/', trim($breadcrumbs ?? ''));
                 return $title . sprintf('<p class="small cms-list__item-breadcrumbs">%s</p>', $breadcrumbs);
             }
         ]);
@@ -1752,7 +1752,7 @@ public function save($data, $form)
 
         // Existing or new record?
         $id = $data['ID'];
-        if (substr($id, 0, 3) != 'new') {
+        if (substr($id ?? '', 0, 3) != 'new') {
             /** @var SiteTree $record */
             $record = DataObject::get_by_id($className, $id);
             // Check edit permissions
@@ -1810,7 +1810,7 @@ public function save($data, $form)
             );
         }
 
-        $this->getResponse()->addHeader('X-Status', rawurlencode($message));
+        $this->getResponse()->addHeader('X-Status', rawurlencode($message ?? ''));
         return $this->getResponseNegotiator()->respond($this->getRequest());
     }
 
@@ -1825,9 +1825,9 @@ public function save($data, $form)
     public function getNewItem($id, $setID = true)
     {
         $parentClass = $this->config()->get('tree_class');
-        list(, $className, $parentID) = array_pad(explode('-', $id), 3, null);
+        list(, $className, $parentID) = array_pad(explode('-', $id ?? ''), 3, null);
 
-        if (!is_a($className, $parentClass, true)) {
+        if (!is_a($className, $parentClass ?? '', true)) {
             $response = Security::permissionFailure($this);
             if (!$response) {
                 $response = $this->getResponse();
@@ -1931,7 +1931,7 @@ public function revert($data, $form)
                 "Restored '{title}' successfully",
                 'Param {title} is a title',
                 ['title' => $record->Title]
-            ))
+            ) ?? '')
         );
 
         return $this->getResponseNegotiator()->respond($this->getRequest());
@@ -1967,7 +1967,7 @@ public function delete($data, $form)
                 __CLASS__ . '.REMOVEDPAGEFROMDRAFT',
                 "Removed '{title}' from the draft site",
                 ['title' => $record->Title]
-            ))
+            ) ?? '')
         );
 
         // Even if the record has been deleted from stage and live, it can be viewed in "archive mode"
@@ -2003,7 +2003,7 @@ public function archive($data, $form)
                 __CLASS__ . '.ARCHIVEDPAGE',
                 "Archived page '{title}'",
                 ['title' => $record->Title]
-            ))
+            ) ?? '')
         );
 
         // Even if the record has been deleted from stage and live, it can be viewed in "archive mode"
@@ -2038,7 +2038,7 @@ public function unpublish($data, $form)
                 __CLASS__ . '.REMOVEDPAGE',
                 "Removed '{title}' from the published site",
                 ['title' => $record->Title]
-            ))
+            ) ?? '')
         );
 
         return $this->getResponseNegotiator()->respond($this->getRequest());
@@ -2091,7 +2091,7 @@ public function doRollback($data, $form)
             );
         }
 
-        $this->getResponse()->addHeader('X-Status', rawurlencode($message));
+        $this->getResponse()->addHeader('X-Status', rawurlencode($message ?? ''));
 
         // Can be used in different contexts: In normal page edit view, in which case the redirect won't have any effect.
         // Or in history view, in which case a revert causes the CMS to re-load the edit view.
@@ -2242,7 +2242,7 @@ public function restore($data, $form)
                 __CLASS__ . '.RESTORED',
                 "Restored '{title}' successfully",
                 ['title' => $restoredPage->Title]
-            ))
+            ) ?? '')
         );
 
         return $this->getResponseNegotiator()->respond($this->getRequest());
@@ -2280,7 +2280,7 @@ public function duplicate($request)
                     __CLASS__ . '.DUPLICATED',
                     "Duplicated '{title}' successfully",
                     ['title' => $newPage->Title]
-                ))
+                ) ?? '')
             );
             $url = $newPage->CMSEditLink();
             $this->getResponse()->addHeader('X-ControllerURL', $url);
@@ -2318,7 +2318,7 @@ public function duplicatewithchildren($request)
                     __CLASS__ . '.DUPLICATEDWITHCHILDREN',
                     "Duplicated '{title}' and children successfully",
                     ['title' => $newPage->Title]
-                ))
+                ) ?? '')
             );
             $url = $newPage->CMSEditLink();
             $this->getResponse()->addHeader('X-ControllerURL', $url);
@@ -2370,7 +2370,7 @@ protected function generateHintsCacheKey($memberID)
 
         $this->extend('updateHintsCacheKey', $baseKey);
 
-        return md5($baseKey);
+        return md5($baseKey ?? '');
     }
 
     /**
diff --git a/code/Controllers/CMSPageAddController.php b/code/Controllers/CMSPageAddController.php
index a246826daf..d198d41f38 100644
--- a/code/Controllers/CMSPageAddController.php
+++ b/code/Controllers/CMSPageAddController.php
@@ -112,7 +112,7 @@ public function AddForm()
                 "PageType",
                 DBField::create_field(
                     'HTMLFragment',
-                    sprintf($numericLabelTmpl, 2, _t('SilverStripe\\CMS\\Controllers\\CMSMain.ChoosePageType', 'Choose page type'))
+                    sprintf($numericLabelTmpl ?? '', 2, _t('SilverStripe\\CMS\\Controllers\\CMSMain.ChoosePageType', 'Choose page type'))
                 ),
                 $pageTypes,
                 'Page'
@@ -121,7 +121,7 @@ public function AddForm()
 
         $parentModeField->setTitle(DBField::create_field(
             'HTMLFragment',
-            sprintf($numericLabelTmpl, 1, _t('SilverStripe\\CMS\\Controllers\\CMSMain.ChoosePageParentMode', 'Choose where to create this page'))
+            sprintf($numericLabelTmpl ?? '', 1, _t('SilverStripe\\CMS\\Controllers\\CMSMain.ChoosePageParentMode', 'Choose where to create this page'))
         ));
 
         $parentField->setSearchFunction(function ($sourceObject, $labelField, $search) {
diff --git a/code/Controllers/CMSPagesController.php b/code/Controllers/CMSPagesController.php
index 4c9a9e6edb..5fc962a977 100644
--- a/code/Controllers/CMSPagesController.php
+++ b/code/Controllers/CMSPagesController.php
@@ -55,7 +55,7 @@ public function Breadcrumbs($unlinked = false)
                     $params['ParentID'] = $page->ID;
                     $item = new stdClass();
                     $item->Title = $page->Title;
-                    $item->Link = Controller::join_links($this->Link(), '?' . http_build_query($params));
+                    $item->Link = Controller::join_links($this->Link(), '?' . http_build_query($params ?? []));
                     $items->push(new ArrayData($item));
                 }
             }
diff --git a/code/Controllers/CMSSiteTreeFilter.php b/code/Controllers/CMSSiteTreeFilter.php
index 92e73c2a3b..d73fe96456 100644
--- a/code/Controllers/CMSSiteTreeFilter.php
+++ b/code/Controllers/CMSSiteTreeFilter.php
@@ -90,7 +90,7 @@ public static function get_all_filters()
         uasort($filterMap, function ($a, $b) {
             return ($a === CMSSiteTreeFilter_Search::title())
                 ? -1
-                : strcasecmp($a, $b);
+                : strcasecmp($a ?? '', $b ?? '');
         });
 
         return $filterMap;
@@ -164,7 +164,7 @@ protected function populateIDs()
 
             while (!empty($parents)) {
                 $q = Versioned::get_including_deleted(SiteTree::class)
-                    ->byIDs(array_keys($parents));
+                    ->byIDs(array_keys($parents ?? []));
                 $list = $q->map('ID', 'ParentID');
                 $parents = [];
                 foreach ($list as $id => $parentID) {
diff --git a/code/Controllers/ContentController.php b/code/Controllers/ContentController.php
index 19e9eada18..3fcb51f972 100644
--- a/code/Controllers/ContentController.php
+++ b/code/Controllers/ContentController.php
@@ -156,7 +156,7 @@ protected function init()
             $getVars = $_GET;
             unset($getVars['url']);
             if ($getVars) {
-                $url = "?" . http_build_query($getVars);
+                $url = "?" . http_build_query($getVars ?? []);
             } else {
                 $url = "";
             }
@@ -494,7 +494,7 @@ public function successfullyinstalled()
         // TODO Allow this to work when allow_url_fopen=0
         if (isset($_SESSION['StatsID']) && $_SESSION['StatsID']) {
             $url = 'http://ss2stat.silverstripe.com/Installation/installed?ID=' . $_SESSION['StatsID'];
-            @file_get_contents($url);
+            @file_get_contents($url ?? '');
         }
 
         global $project;
@@ -532,11 +532,11 @@ public function deleteinstallfiles()
         $unsuccessful = new ArrayList();
         foreach ($installfiles as $installfile) {
             $installfilepath = PUBLIC_PATH . '/' . $installfile;
-            if (file_exists($installfilepath)) {
-                @unlink($installfilepath);
+            if (file_exists($installfilepath ?? '')) {
+                @unlink($installfilepath ?? '');
             }
 
-            if (file_exists($installfilepath)) {
+            if (file_exists($installfilepath ?? '')) {
                 $unsuccessful->push(new ArrayData(['File' => $installfile]));
             }
         }
diff --git a/code/Controllers/ModelAsController.php b/code/Controllers/ModelAsController.php
index c266b45c42..8f9233ca65 100644
--- a/code/Controllers/ModelAsController.php
+++ b/code/Controllers/ModelAsController.php
@@ -41,8 +41,8 @@ public static function controller_for(SiteTree $sitetree, $action = null)
     {
         $controller = $sitetree->getControllerName();
 
-        if ($action && class_exists($controller . '_' . ucfirst($action))) {
-            $controller = $controller . '_' . ucfirst($action);
+        if ($action && class_exists($controller . '_' . ucfirst($action ?? ''))) {
+            $controller = $controller . '_' . ucfirst($action ?? '');
         }
 
         return Injector::inst()->create($controller, $sitetree);
@@ -131,7 +131,7 @@ public function getNestedController()
         // url encode unless it's multibyte (already pre-encoded in the database)
         $filter = URLSegmentFilter::create();
         if (!$filter->getAllowMultibyte()) {
-            $URLSegment = rawurlencode($URLSegment);
+            $URLSegment = rawurlencode($URLSegment ?? '');
         }
 
         // Select child page
diff --git a/code/Controllers/OldPageRedirector.php b/code/Controllers/OldPageRedirector.php
index 52f8ad7331..5e526e1125 100644
--- a/code/Controllers/OldPageRedirector.php
+++ b/code/Controllers/OldPageRedirector.php
@@ -23,8 +23,8 @@ class OldPageRedirector extends Extension
     public function onBeforeHTTPError404($request)
     {
         // We need to get the URL ourselves because $request->allParams() only has a max of 4 params
-        $params = preg_split('|/+|', $request->getURL());
-        $cleanURL = trim(Director::makeRelative($request->getURL(false)), '/');
+        $params = preg_split('|/+|', $request->getURL() ?? '');
+        $cleanURL = trim(Director::makeRelative($request->getURL(false)) ?? '', '/');
 
         $getvars = $request->getVars();
         unset($getvars['url']);
@@ -33,7 +33,7 @@ public function onBeforeHTTPError404($request)
         if (!$page) {
             $page = self::find_old_page($params);
         }
-        $cleanPage = trim(Director::makeRelative($page), '/');
+        $cleanPage = trim(Director::makeRelative($page) ?? '', '/');
         if (!$cleanPage) {
             $cleanPage = Director::makeRelative(RootURLController::get_homepage_link());
         }
@@ -64,7 +64,7 @@ public static function find_old_page($params, $parent = null, $redirect = false)
     {
         $parent = is_numeric($parent) && $parent > 0 ? SiteTree::get()->byID($parent) : $parent;
         $params = (array)$params;
-        $URL = rawurlencode(array_shift($params));
+        $URL = rawurlencode(array_shift($params) ?? '');
         if (empty($URL)) {
             return false;
         }
@@ -93,7 +93,7 @@ public static function find_old_page($params, $parent = null, $redirect = false)
         }
 
         if ($page && $page->canView()) {
-            if (count($params)) {
+            if (count($params ?? [])) {
                 // We have to go deeper!
                 $ret = self::find_old_page($params, $page, $redirect);
                 if ($ret) {
diff --git a/code/Controllers/RootURLController.php b/code/Controllers/RootURLController.php
index f7641d34e9..e8522989f7 100644
--- a/code/Controllers/RootURLController.php
+++ b/code/Controllers/RootURLController.php
@@ -56,7 +56,7 @@ public static function get_homepage_link()
      */
     public static function should_be_on_root(SiteTree $page)
     {
-        return (!self::$is_at_root && self::get_homepage_link() == trim($page->RelativeLink(true), '/'));
+        return (!self::$is_at_root && self::get_homepage_link() == trim($page->RelativeLink(true) ?? '', '/'));
     }
 
     /**
diff --git a/code/Controllers/SilverStripeNavigator.php b/code/Controllers/SilverStripeNavigator.php
index 2f5db31b83..dce05372ab 100644
--- a/code/Controllers/SilverStripeNavigator.php
+++ b/code/Controllers/SilverStripeNavigator.php
@@ -67,7 +67,7 @@ public function getItems()
         ksort($items);
 
         // Drop the keys and let the ArrayList handle the numbering, so $First, $Last and others work properly.
-        return new ArrayList(array_values($items));
+        return new ArrayList(array_values($items ?? []));
     }
 
     /**
diff --git a/code/Controllers/SilverStripeNavigatorItem_ArchiveLink.php b/code/Controllers/SilverStripeNavigatorItem_ArchiveLink.php
index b573b183a6..00dab1379d 100644
--- a/code/Controllers/SilverStripeNavigatorItem_ArchiveLink.php
+++ b/code/Controllers/SilverStripeNavigatorItem_ArchiveLink.php
@@ -20,7 +20,7 @@ public function getHTML()
         $linkTitle = _t('SilverStripe\\CMS\\Controllers\\ContentController.ARCHIVEDSITE', 'Preview version');
         $recordLink = Convert::raw2att(Controller::join_links(
             $this->record->AbsoluteLink(),
-            '?archiveDate=' . urlencode($this->record->LastEdited)
+            '?archiveDate=' . urlencode($this->record->LastEdited ?? '')
         ));
         return "<a class=\"{$linkClass}\" href=\"$recordLink\" target=\"_blank\">$linkTitle</a>";
     }
@@ -48,7 +48,7 @@ public function getLink()
     {
         return Controller::join_links(
             $this->record->PreviewLink(),
-            '?archiveDate=' . urlencode($this->record->LastEdited)
+            '?archiveDate=' . urlencode($this->record->LastEdited ?? '')
         );
     }
 
diff --git a/code/Forms/SiteTreeURLSegmentField.php b/code/Forms/SiteTreeURLSegmentField.php
index 2e3a44b0eb..c493018232 100644
--- a/code/Forms/SiteTreeURLSegmentField.php
+++ b/code/Forms/SiteTreeURLSegmentField.php
@@ -44,7 +44,7 @@ class SiteTreeURLSegmentField extends TextField
 
     public function Value()
     {
-        return rawurldecode($this->value);
+        return rawurldecode($this->value ?? '');
     }
 
     public function getAttributes()
@@ -82,7 +82,7 @@ public function suggest($request)
         $page->URLSegment = $page->generateURLSegment($request->getVar('value'));
         $count = 2;
         while (!$page->validURLSegment()) {
-            $page->URLSegment = preg_replace('/-[0-9]+$/', '', $page->URLSegment) . '-' . $count;
+            $page->URLSegment = preg_replace('/-[0-9]+$/', '', $page->URLSegment ?? '') . '-' . $count;
             $count++;
         }
 
diff --git a/code/Model/RedirectorPage.php b/code/Model/RedirectorPage.php
index 95b0dec3e9..97572142e7 100644
--- a/code/Model/RedirectorPage.php
+++ b/code/Model/RedirectorPage.php
@@ -173,8 +173,8 @@ protected function onBeforeWrite()
     {
         parent::onBeforeWrite();
 
-        if ($this->ExternalURL && substr($this->ExternalURL, 0, 2) !== '//') {
-            $urlParts = parse_url($this->ExternalURL);
+        if ($this->ExternalURL && substr($this->ExternalURL ?? '', 0, 2) !== '//') {
+            $urlParts = parse_url($this->ExternalURL ?? '');
             if ($urlParts) {
                 if (empty($urlParts['scheme'])) {
                     // no scheme, assume http
diff --git a/code/Model/SiteTree.php b/code/Model/SiteTree.php
index 458ec9c52b..e44dc2472c 100755
--- a/code/Model/SiteTree.php
+++ b/code/Model/SiteTree.php
@@ -430,16 +430,16 @@ public static function get_by_link($link, $cache = true)
         $urlSegmentExpr = sprintf('"%s"."URLSegment"', $tableName);
         $parentIDExpr = sprintf('"%s"."ParentID"', $tableName);
 
-        $link = trim(Director::makeRelative($link), '/');
+        $link = trim(Director::makeRelative($link) ?? '', '/');
         if (!$link) {
             $link = RootURLController::get_homepage_link();
         }
 
-        $parts = preg_split('|/+|', $link);
+        $parts = preg_split('|/+|', $link ?? '');
 
         // Grab the initial root level page to traverse down from.
         $URLSegment = array_shift($parts);
-        $conditions = [$urlSegmentExpr => rawurlencode($URLSegment)];
+        $conditions = [$urlSegmentExpr => rawurlencode($URLSegment ?? '')];
         if (self::config()->get('nested_urls')) {
             $conditions[] = [$parentIDExpr => 0];
         }
@@ -474,7 +474,7 @@ public static function get_by_link($link, $cache = true)
         }
 
         // Check if we have any more URL parts to parse.
-        if (!self::config()->get('nested_urls') || !count($parts)) {
+        if (!self::config()->get('nested_urls') || !count($parts ?? [])) {
             return $sitetree;
         }
 
@@ -521,7 +521,7 @@ public static function page_type_classes()
     {
         $classes = ClassInfo::getValidSubClasses();
 
-        $baseClassIndex = array_search(self::class, $classes);
+        $baseClassIndex = array_search(self::class, $classes ?? []);
         if ($baseClassIndex !== false) {
             unset($classes[$baseClassIndex]);
         }
@@ -542,10 +542,10 @@ public static function page_type_classes()
         // If any of the descendents don't want any of the elders to show up, cruelly render the elders surplus to
         // requirements
         if ($kill_ancestors) {
-            $kill_ancestors = array_unique($kill_ancestors);
+            $kill_ancestors = array_unique($kill_ancestors ?? []);
             foreach ($kill_ancestors as $mark) {
                 // unset from $classes
-                $idx = array_search($mark, $classes, true);
+                $idx = array_search($mark, $classes ?? [], true);
                 if ($idx !== false) {
                     unset($classes[$idx]);
                 }
@@ -733,7 +733,7 @@ public function CMSEditLink()
      */
     public function ElementName()
     {
-        return str_replace('/', '-', trim($this->RelativeLink(true), '/'));
+        return str_replace('/', '-', trim($this->RelativeLink(true) ?? '', '/'));
     }
 
     /**
@@ -762,7 +762,7 @@ public function isCurrent()
     public function isSection()
     {
         return $this->isCurrent() || (
-            Director::get_current_page() instanceof SiteTree && in_array($this->ID, Director::get_current_page()->getAncestors()->column())
+            Director::get_current_page() instanceof SiteTree && in_array($this->ID, Director::get_current_page()->getAncestors()->column() ?? [])
         );
     }
 
@@ -931,7 +931,7 @@ public function getBreadcrumbItems($maxDepth = 20, $stopAtPageType = false, $sho
 
         while ($page
             && $page->exists()
-            && (!$maxDepth || count($pages) < $maxDepth)
+            && (!$maxDepth || count($pages ?? []) < $maxDepth)
             && (!$stopAtPageType || $page->ClassName != $stopAtPageType)
         ) {
             if ($showHidden || $page->ShowInMenus || ($page->ID == $this->ID)) {
@@ -941,7 +941,7 @@ public function getBreadcrumbItems($maxDepth = 20, $stopAtPageType = false, $sho
             $page = $page->Parent();
         }
 
-        return new ArrayList(array_reverse($pages));
+        return new ArrayList(array_reverse($pages ?? []));
     }
 
 
@@ -1013,7 +1013,7 @@ public function NestedTitle($level = 2, $separator = " - ")
             $item = $item->getParent();
             $level--;
         }
-        return implode($separator, array_reverse($parts));
+        return implode($separator ?? '', array_reverse($parts ?? []));
     }
 
     /**
@@ -1043,8 +1043,8 @@ public function can($perm, $member = null, $context = [])
             return true;
         }
 
-        if (is_string($perm) && method_exists($this, 'can' . ucfirst($perm))) {
-            $method = 'can' . ucfirst($perm);
+        if (is_string($perm) && method_exists($this, 'can' . ucfirst($perm ?? ''))) {
+            $method = 'can' . ucfirst($perm ?? '');
             return $this->$method($member);
         }
 
@@ -1266,7 +1266,7 @@ public function canCreate($member = null, $context = [])
         // Block children not allowed for this parent type
         $parent = isset($context['Parent']) ? $context['Parent'] : null;
         $strictParentInstance = ($parent && $parent instanceof SiteTree);
-        if ($strictParentInstance && !in_array(static::class, $parent->allowedChildren())) {
+        if ($strictParentInstance && !in_array(static::class, $parent->allowedChildren() ?? [])) {
             return false;
         }
 
@@ -1341,7 +1341,7 @@ public function canEdit($member = null)
     public function getSiteConfig()
     {
         $configs = $this->invokeWithExtensions('alternateSiteConfig');
-        foreach (array_filter($configs) as $config) {
+        foreach (array_filter($configs ?? []) as $config) {
             return $config;
         }
 
@@ -1472,7 +1472,7 @@ public function MetaComponents()
      */
     private function getGenerator(): string
     {
-        $generator = trim(Config::inst()->get(self::class, 'meta_generator'));
+        $generator = trim(Config::inst()->get(self::class, 'meta_generator') ?? '');
         if ($generator === '') {
             return '';
         }
@@ -1480,7 +1480,7 @@ private function getGenerator(): string
             $version = $this->getVersionProvider()->getModuleVersion('silverstripe/framework');
             // Only include stable version numbers so as not to clutter any aggregate reports
             // with non-standard versions e.g. forks
-            if (preg_match('#^([0-9]+\.[0-9]+)\.[0-9]+$#', $version, $m)) {
+            if (preg_match('#^([0-9]+\.[0-9]+)\.[0-9]+$#', $version ?? '', $m)) {
                 $generator .= ' ' . $m[1];
             }
         }
@@ -1517,7 +1517,7 @@ public function MetaTags($includeTitle = true)
     {
         $tags = [];
         $tagsArray = $this->MetaComponents();
-        if (!$includeTitle || strtolower($includeTitle) == 'false') {
+        if (!$includeTitle || strtolower($includeTitle ?? '') == 'false') {
             unset($tagsArray['title']);
         }
 
@@ -1652,19 +1652,19 @@ protected function onBeforeWrite()
         // Ensure that this object has a non-conflicting URLSegment value.
         $count = 2;
         while (!$this->validURLSegment()) {
-            $this->URLSegment = preg_replace('/-[0-9]+$/', '', $this->URLSegment) . '-' . $count;
+            $this->URLSegment = preg_replace('/-[0-9]+$/', '', $this->URLSegment ?? '') . '-' . $count;
             $count++;
         }
 
         // Check to see if we've only altered fields that shouldn't affect versioning
         $fieldsIgnoredByVersioning = ['HasBrokenLink', 'Status', 'HasBrokenFile', 'ToDo', 'VersionID', 'SaveCount'];
-        $changedFields = array_keys($this->getChangedFields(true, 2));
+        $changedFields = array_keys($this->getChangedFields(true, 2) ?? []);
 
         // This more rigorous check is inline with the test that write() does to decide whether or not to write to the
         // DB. We use that to avoid cluttering the system with a migrateVersion() call that doesn't get used
-        $oneChangedFields = array_keys($this->getChangedFields(true, 1));
+        $oneChangedFields = array_keys($this->getChangedFields(true, 1) ?? []);
 
-        if ($oneChangedFields && !array_diff($changedFields, $fieldsIgnoredByVersioning)) {
+        if ($oneChangedFields && !array_diff($changedFields ?? [], $fieldsIgnoredByVersioning)) {
             $this->setNextWriteWithoutVersion(true);
         }
 
@@ -1755,7 +1755,7 @@ public function validate()
             $subject = ($this instanceof VirtualPage && $this->CopyContentFromID)
                 ? $this->CopyContentFrom()
                 : $this;
-            if (!in_array($subject->ClassName, $allowed)) {
+            if (!in_array($subject->ClassName, $allowed ?? [])) {
                 $result->addError(
                     _t(
                         'SilverStripe\\CMS\\Model\\SiteTree.PageTypeNotAllowed',
@@ -1804,7 +1804,7 @@ public function validURLSegment()
                     return false;
                 }
             }
-        } elseif (in_array(strtolower($this->URLSegment), $this->getExcludedURLSegments())) {
+        } elseif (in_array(strtolower($this->URLSegment ?? ''), $this->getExcludedURLSegments() ?? [])) {
             // Guard against url segments for the base page
             // Default to '-2', onBeforeWrite takes care of further possible clashes
             return false;
@@ -2276,7 +2276,7 @@ public function getSettingsFields()
             $viewerGroupsField->setDescription(_t(
                 'SilverStripe\\CMS\\Model\\SiteTree.VIEWER_GROUPS_FIELD_DESC',
                 'Groups with global view permissions: {groupList}',
-                ['groupList' => implode(', ', array_values($viewAllGroupsMap))]
+                ['groupList' => implode(', ', array_values($viewAllGroupsMap ?? []))]
             ));
         }
 
@@ -2284,7 +2284,7 @@ public function getSettingsFields()
             $editorGroupsField->setDescription(_t(
                 'SilverStripe\\CMS\\Model\\SiteTree.EDITOR_GROUPS_FIELD_DESC',
                 'Groups with global edit permissions: {groupList}',
-                ['groupList' => implode(', ', array_values($editAllGroupsMap))]
+                ['groupList' => implode(', ', array_values($editAllGroupsMap ?? []))]
             ));
         }
 
@@ -2622,7 +2622,7 @@ public function isNew()
             return false;
         }
 
-        return stripos($this->ID, 'new') === 0;
+        return stripos($this->ID ?? '', 'new') === 0;
     }
 
     /**
@@ -2673,9 +2673,9 @@ protected function getClassDropdown()
         if ($currentClass) {
             $currentPageTypeName = $result[$currentClass];
             unset($result[$currentClass]);
-            $result = array_reverse($result);
+            $result = array_reverse($result ?? []);
             $result[$currentClass] = $currentPageTypeName;
-            $result = array_reverse($result);
+            $result = array_reverse($result ?? []);
         }
 
         return $result;
@@ -2699,7 +2699,7 @@ public function allowedChildren()
                     $candidates = Config::inst()->get($class, 'allowed_children', Config::UNINHERITED);
                     break;
                 }
-                $class = get_parent_class($class);
+                $class = get_parent_class($class ?? '');
             }
             if (!$candidates || $candidates === 'none' || $candidates === 'SiteTree_root') {
                 return [];
@@ -2710,8 +2710,8 @@ public function allowedChildren()
             foreach ((array)$candidates as $candidate) {
                 // If a classname is prefixed by "*", such as "*Page", then only that class is allowed - no subclasses.
                 // Otherwise, the class and all its subclasses are allowed.
-                if (substr($candidate, 0, 1) == '*') {
-                    $allowedChildren[] = substr($candidate, 1);
+                if (substr($candidate ?? '', 0, 1) == '*') {
+                    $allowedChildren[] = substr($candidate ?? '', 1);
                 } elseif (($candidate !== 'SiteTree_root')
                     && ($subclasses = ClassInfo::subclassesFor($candidate))
                 ) {
@@ -2802,7 +2802,7 @@ public function defaultChild()
         $default = $this->config()->get('default_child');
         $allowed = $this->allowedChildren();
         if ($allowed) {
-            if (!$default || !in_array($default, $allowed)) {
+            if (!$default || !in_array($default, $allowed ?? [])) {
                 $default = reset($allowed);
             }
             return $default;
@@ -2929,7 +2929,7 @@ public function getTreeTitle()
             Convert::raw2htmlid(static::class),
             $this->isHomePage() ? ' homepage' : '',
             Convert::raw2att(json_encode($children)),
-            Convert::raw2xml(str_replace(["\n","\r"], "", $this->MenuTitle))
+            Convert::raw2xml(str_replace(["\n","\r"], "", $this->MenuTitle ?? ''))
         );
         foreach ($flags as $class => $data) {
             if (is_string($data)) {
@@ -3143,7 +3143,7 @@ public function getPageIconURL()
         if (!$icon) {
             return null;
         }
-        if (strpos($icon, 'data:image/') !== false) {
+        if (strpos($icon ?? '', 'data:image/') !== false) {
             return $icon;
         }
 
@@ -3284,15 +3284,15 @@ protected function getExcludedURLSegments()
 
         // Build from rules
         foreach (Director::config()->get('rules') as $pattern => $rule) {
-            $route = explode('/', $pattern);
-            if (!empty($route) && strpos($route[0], '$') === false) {
-                $excludes[] = strtolower($route[0]);
+            $route = explode('/', $pattern ?? '');
+            if (!empty($route) && strpos($route[0] ?? '', '$') === false) {
+                $excludes[] = strtolower($route[0] ?? '');
             }
         }
 
         // Build from base folders
         foreach (glob(Director::publicFolder() . '/*', GLOB_ONLYDIR) as $folder) {
-            $excludes[] = strtolower(basename($folder));
+            $excludes[] = strtolower(basename($folder ?? ''));
         }
 
         $this->extend('updateExcludedURLSegments', $excludes);
@@ -3306,7 +3306,7 @@ public function getAnchorsOnPage()
     {
         $parseSuccess = preg_match_all(
             "/\\s+(name|id)\\s*=\\s*([\"'])([^\\2\\s>]*?)\\2|\\s+(name|id)\\s*=\\s*([^\"']+)[\\s +>]/im",
-            $this->Content,
+            $this->Content ?? '',
             $matches
         );
 
diff --git a/code/Model/SiteTreeFolderExtension.php b/code/Model/SiteTreeFolderExtension.php
index 05d827ee87..164b66600c 100644
--- a/code/Model/SiteTreeFolderExtension.php
+++ b/code/Model/SiteTreeFolderExtension.php
@@ -41,7 +41,7 @@ public function getUnusedFilesListFilter()
 
         // Get all classes that aren't folder
         $fileClasses = array_diff_key(
-            ClassInfo::subclassesFor(File::class),
+            ClassInfo::subclassesFor(File::class) ?? [],
             ClassInfo::subclassesFor(Folder::class)
         );
 
@@ -58,7 +58,7 @@ public function getUnusedFilesListFilter()
             $where = [];
             $columns = [];
             foreach ($hasOnes as $relName => $joinClass) {
-                if (in_array($joinClass, $fileClasses)) {
+                if (in_array($joinClass, $fileClasses ?? [])) {
                     $column = $relName . 'ID';
                     $columns[] = $column;
                     $quotedColumn = $schema->sqlColumnForField($className, $column);
diff --git a/code/Model/SiteTreeLinkTracking.php b/code/Model/SiteTreeLinkTracking.php
index c3c2111d5e..c9b53826e0 100644
--- a/code/Model/SiteTreeLinkTracking.php
+++ b/code/Model/SiteTreeLinkTracking.php
@@ -190,13 +190,13 @@ public function trackLinksInField($fieldName, &$anyBroken = false)
     protected function toggleElementClass(DOMElement $domReference, $class, $toggle)
     {
         // Get all existing classes.
-        $classes = array_filter(explode(' ', trim($domReference->getAttribute('class'))));
+        $classes = array_filter(explode(' ', trim($domReference->getAttribute('class') ?? '')));
 
         // Add or remove the broken class from the link, depending on the link status.
         if ($toggle) {
             $classes = array_unique(array_merge($classes, [$class]));
         } else {
-            $classes = array_diff($classes, [$class]);
+            $classes = array_diff($classes ?? [], [$class]);
         }
 
         if (!empty($classes)) {
diff --git a/code/Model/SiteTreeLinkTracking_Parser.php b/code/Model/SiteTreeLinkTracking_Parser.php
index 16ac823b04..857c6c12ab 100644
--- a/code/Model/SiteTreeLinkTracking_Parser.php
+++ b/code/Model/SiteTreeLinkTracking_Parser.php
@@ -59,7 +59,7 @@ public function process(HTMLValue $htmlValue)
 
             // Link to a page on this site.
             $matches = [];
-            if (preg_match('/\[sitetree_link(?:\s*|%20|,)?id=(?<id>[0-9]+)\](#(?<anchor>.*))?/i', $href, $matches)) {
+            if (preg_match('/\[sitetree_link(?:\s*|%20|,)?id=(?<id>[0-9]+)\](#(?<anchor>.*))?/i', $href ?? '', $matches)) {
                 // Check if page link is broken
                 /** @var SiteTree $page */
                 $page = DataObject::get_by_id(SiteTree::class, $matches['id']);
@@ -68,7 +68,7 @@ public function process(HTMLValue $htmlValue)
                     $broken = true;
                 } elseif (!empty($matches['anchor'])) {
                     // Ensure anchor isn't broken on target page
-                    $broken = !in_array($matches['anchor'], $page->getAnchorsOnPage());
+                    $broken = !in_array($matches['anchor'], $page->getAnchorsOnPage() ?? []);
                 } else {
                     $broken = false;
                 }
@@ -85,14 +85,14 @@ public function process(HTMLValue $htmlValue)
             }
 
             // Local anchor.
-            if (preg_match('/^#(.*)/i', $href, $matches)) {
-                $anchor = preg_quote($matches[1], '#');
+            if (preg_match('/^#(.*)/i', $href ?? '', $matches)) {
+                $anchor = preg_quote($matches[1] ?? '', '#');
                 $results[] = [
                     'Type' => 'localanchor',
                     'Target' => null,
                     'Anchor' => $matches[1],
                     'DOMReference' => $link,
-                    'Broken' => !preg_match("#(name|id)=\"{$anchor}\"#", $htmlValue->getContent())
+                    'Broken' => !preg_match("#(name|id)=\"{$anchor}\"#", $htmlValue->getContent() ?? '')
                 ];
 
                 continue;
diff --git a/code/Model/VirtualPage.php b/code/Model/VirtualPage.php
index 2219225b95..dd4187cc01 100644
--- a/code/Model/VirtualPage.php
+++ b/code/Model/VirtualPage.php
@@ -96,9 +96,9 @@ public function getVirtualFields()
         }
 
         // Diff db with non-virtual fields
-        $fields = array_keys(static::getSchema()->fieldSpecs($record));
+        $fields = array_keys(static::getSchema()->fieldSpecs($record) ?? []);
         $nonVirtualFields = $this->getNonVirtualisedFields();
-        return array_diff($fields, $nonVirtualFields);
+        return array_diff($fields ?? [], $nonVirtualFields);
     }
 
     /**
@@ -448,7 +448,7 @@ public function isFieldVirtualised($field)
     {
         // Don't defer if field is non-virtualised
         $ignore = $this->getNonVirtualisedFields();
-        if (in_array($field, $ignore)) {
+        if (in_array($field, $ignore ?? [])) {
             return false;
         }
 
@@ -474,7 +474,7 @@ public function __call($method, $args)
         if (parent::hasMethod($method)) {
             return parent::__call($method, $args);
         } else {
-            return call_user_func_array([$this->CopyContentFrom(), $method], $args);
+            return call_user_func_array([$this->CopyContentFrom(), $method], $args ?? []);
         }
     }
 
diff --git a/code/Reports/BrokenFilesReport.php b/code/Reports/BrokenFilesReport.php
index 3b1bfcc7cf..609428c328 100644
--- a/code/Reports/BrokenFilesReport.php
+++ b/code/Reports/BrokenFilesReport.php
@@ -29,7 +29,7 @@ public function sourceRecords($params = null)
     {
         // Get class names for page types that are not virtual pages or redirector pages
         $classes = array_diff(
-            ClassInfo::subclassesFor(SiteTree::class),
+            ClassInfo::subclassesFor(SiteTree::class) ?? [],
             ClassInfo::subclassesFor(VirtualPage::class),
             ClassInfo::subclassesFor(RedirectorPage::class)
         );
diff --git a/code/Reports/BrokenLinksReport.php b/code/Reports/BrokenLinksReport.php
index 796df87447..4490658ab1 100644
--- a/code/Reports/BrokenLinksReport.php
+++ b/code/Reports/BrokenLinksReport.php
@@ -33,7 +33,7 @@ public function sourceRecords($params, $sort, $limit)
         $join = '';
         $sortBrokenReason = false;
         if ($sort) {
-            $parts = explode(' ', $sort);
+            $parts = explode(' ', $sort ?? '');
             $field = $parts[0];
             $direction = $parts[1];
 
@@ -93,7 +93,7 @@ public function sourceRecords($params, $sort, $limit)
                 }
 
                 if ($reason) {
-                    if (isset($params['Reason']) && $params['Reason'] && !in_array($params['Reason'], $reasonCodes)) {
+                    if (isset($params['Reason']) && $params['Reason'] && !in_array($params['Reason'], $reasonCodes ?? [])) {
                         continue;
                     }
                     $record->BrokenReason = $reason;
diff --git a/code/Search/SearchForm.php b/code/Search/SearchForm.php
index 12f81534db..7bb6654e2e 100644
--- a/code/Search/SearchForm.php
+++ b/code/Search/SearchForm.php
@@ -98,14 +98,14 @@ public function __construct(
     public function classesToSearch($classes)
     {
         $supportedClasses = [SiteTree::class, File::class];
-        $illegalClasses = array_diff($classes, $supportedClasses);
+        $illegalClasses = array_diff($classes ?? [], $supportedClasses);
         if ($illegalClasses) {
             throw new BadMethodCallException(
                 "SearchForm::classesToSearch() passed illegal classes '" . implode("', '", $illegalClasses)
                 . "'.  At this stage, only File and SiteTree are allowed"
             );
         }
-        $legalClasses = array_intersect($classes, $supportedClasses);
+        $legalClasses = array_intersect($classes ?? [], $supportedClasses);
         $this->classesToSearch = $legalClasses;
     }
 
@@ -155,10 +155,10 @@ public function getResults()
             return ' -' . $matches[3];
         };
 
-        $keywords = preg_replace_callback('/()("[^()"]+")( and )("[^"()]+")()/i', $andProcessor, $keywords);
-        $keywords = preg_replace_callback('/(^| )([^() ]+)( and )([^ ()]+)( |$)/i', $andProcessor, $keywords);
-        $keywords = preg_replace_callback('/(^| )(not )("[^"()]+")/i', $notProcessor, $keywords);
-        $keywords = preg_replace_callback('/(^| )(not )([^() ]+)( |$)/i', $notProcessor, $keywords);
+        $keywords = preg_replace_callback('/()("[^()"]+")( and )("[^"()]+")()/i', $andProcessor, $keywords ?? '');
+        $keywords = preg_replace_callback('/(^| )([^() ]+)( and )([^ ()]+)( |$)/i', $andProcessor, $keywords ?? '');
+        $keywords = preg_replace_callback('/(^| )(not )("[^"()]+")/i', $notProcessor, $keywords ?? '');
+        $keywords = preg_replace_callback('/(^| )(not )([^() ]+)( |$)/i', $notProcessor, $keywords ?? '');
 
         $keywords = $this->addStarsToKeywords($keywords);
 
@@ -166,10 +166,10 @@ public function getResults()
         $start = max(0, (int)$request->requestVar('start'));
 
         $booleanSearch =
-            strpos($keywords, '"') !== false ||
-            strpos($keywords, '+') !== false ||
-            strpos($keywords, '-') !== false ||
-            strpos($keywords, '*') !== false;
+            strpos($keywords ?? '', '"') !== false ||
+            strpos($keywords ?? '', '+') !== false ||
+            strpos($keywords ?? '', '-') !== false ||
+            strpos($keywords ?? '', '*') !== false;
         $results = DB::get_conn()->searchEngine($this->classesToSearch, $keywords, $start, $pageLength, "\"Relevance\" DESC", "", $booleanSearch);
 
         // filter by permission
@@ -197,19 +197,19 @@ public function getResults()
 
     protected function addStarsToKeywords($keywords)
     {
-        if (!trim($keywords)) {
+        if (!trim($keywords ?? '')) {
             return "";
         }
         // Add * to each keyword
-        $splitWords = preg_split("/ +/", trim($keywords));
+        $splitWords = preg_split("/ +/", trim($keywords ?? ''));
         $newWords = [];
-        for ($i = 0; $i < count($splitWords); $i++) {
+        for ($i = 0; $i < count($splitWords ?? []); $i++) {
             $word = $splitWords[$i];
             if ($word[0] == '"') {
-                while (++$i < count($splitWords)) {
+                while (++$i < count($splitWords ?? [])) {
                     $subword = $splitWords[$i];
                     $word .= ' ' . $subword;
-                    if (substr($subword, -1) == '"') {
+                    if (substr($subword ?? '', -1) == '"') {
                         break;
                     }
                 }
diff --git a/tests/behat/src/LoginContext.php b/tests/behat/src/LoginContext.php
index 93d982a879..44fb3c04fc 100644
--- a/tests/behat/src/LoginContext.php
+++ b/tests/behat/src/LoginContext.php
@@ -25,7 +25,7 @@ public function pagesShouldBeEditableBy($negative, $permCode)
         $email = "{$permCode}@example.org";
         $password = 'Password!456';
         $member = $this->generateMemberWithPermission($email, $password, $permCode);
-        $canEdit = strstr($negative, 'not') ? false : true;
+        $canEdit = strstr($negative ?? '', 'not') ? false : true;
 
         if ($canEdit) {
             Assert::assertTrue($page->canEdit($member), 'The member can edit this page');
diff --git a/tests/behat/src/ThemeContext.php b/tests/behat/src/ThemeContext.php
index a7dc6a6d0f..ead1f8265d 100644
--- a/tests/behat/src/ThemeContext.php
+++ b/tests/behat/src/ThemeContext.php
@@ -23,7 +23,7 @@ class ThemeContext implements Context
      */
     public function stepCreateTheme($theme)
     {
-        if (!preg_match('/^[0-9a-zA-Z_-]+$/', $theme)) {
+        if (!preg_match('/^[0-9a-zA-Z_-]+$/', $theme ?? '')) {
             throw new \InvalidArgumentException("Bad theme '$theme'");
         }
 
@@ -42,10 +42,10 @@ public function stepCreateTheme($theme)
      */
     public function stepCreateTemplate($template, $theme, $content)
     {
-        if (!preg_match('/^[0-9a-zA-Z_-]+$/', $theme)) {
+        if (!preg_match('/^[0-9a-zA-Z_-]+$/', $theme ?? '')) {
             throw new \InvalidArgumentException("Bad theme '$theme'");
         }
-        if (!preg_match('/^(Layout\/)?[0-9a-zA-Z_-]+\.ss$/', $template)) {
+        if (!preg_match('/^(Layout\/)?[0-9a-zA-Z_-]+\.ss$/', $template ?? '')) {
             throw new \InvalidArgumentException("Bad template '$template'");
         }
 
@@ -56,16 +56,16 @@ public function stepCreateTemplate($template, $theme, $content)
     protected function requireFile($filename, $content)
     {
         // Already exists
-        if (file_exists($filename)) {
+        if (file_exists($filename ?? '')) {
             // If the content is different, remember old content for restoration
-            $origContent = file_get_contents($filename);
+            $origContent = file_get_contents($filename ?? '');
             if ($origContent != $content) {
-                file_put_contents($filename, $content);
+                file_put_contents($filename ?? '', $content);
                 $this->restoreFiles[$filename] = $origContent;
             }
         // Doesn't exist, mark it for deletion after test
         } else {
-            file_put_contents($filename, $content);
+            file_put_contents($filename ?? '', $content);
             $this->restoreFiles[$filename] = null;
         }
     }
@@ -73,8 +73,8 @@ protected function requireFile($filename, $content)
     protected function requireDir($dirname)
     {
         // Directory doesn't exist, create it and mark it for deletion
-        if (!file_exists($dirname)) {
-            mkdir($dirname);
+        if (!file_exists($dirname ?? '')) {
+            mkdir($dirname ?? '');
             $this->restoreDirectories[] = $dirname;
         }
     }
@@ -92,9 +92,9 @@ public function cleanThemesAfterScenario()
         if ($this->restoreFiles) {
             foreach ($this->restoreFiles as $file => $origContent) {
                 if ($origContent === null) {
-                    unlink($file);
+                    unlink($file ?? '');
                 } else {
-                    file_put_contents($file, $origContent);
+                    file_put_contents($file ?? '', $origContent);
                 }
             }
 
@@ -104,9 +104,9 @@ public function cleanThemesAfterScenario()
         // Restore any created directories: that is, delete them
         if ($this->restoreDirectories) {
             // Flip the order so that nested direcotires are unlinked() first
-            $this->restoreDirectories = array_reverse($this->restoreDirectories);
+            $this->restoreDirectories = array_reverse($this->restoreDirectories ?? []);
             foreach ($this->restoreDirectories as $dir) {
-                rmdir($dir);
+                rmdir($dir ?? '');
             }
 
             $this->restoreDirectories = [];
diff --git a/tests/bootstrap/app.php b/tests/bootstrap/app.php
index 41372cf8d9..e8412b0fed 100644
--- a/tests/bootstrap/app.php
+++ b/tests/bootstrap/app.php
@@ -6,8 +6,8 @@
 } else {
     $projectPath = getcwd() . '/app';
 }
-if (!is_dir($projectPath)) {
-    mkdir($projectPath, 02775);
+if (!is_dir($projectPath ?? '')) {
+    mkdir($projectPath ?? '', 02775);
     mkdir($projectPath . '/code', 02775);
     mkdir($projectPath . '/_config', 02775);
     copy(__DIR__ . '/fixtures/Page.php.fixture', $projectPath . '/code/Page.php');
diff --git a/tests/php/Controllers/CMSBatchActionsTest.php b/tests/php/Controllers/CMSBatchActionsTest.php
index 441e18b2f8..9a079b8073 100644
--- a/tests/php/Controllers/CMSBatchActionsTest.php
+++ b/tests/php/Controllers/CMSBatchActionsTest.php
@@ -142,7 +142,7 @@ public function testBatchRestore()
         $this->assertEquals($archivedID, $list->first()->ParentID);
 
         // Run restore
-        $result = json_decode($action->run($list), true);
+        $result = json_decode($action->run($list) ?? '', true);
         $this->assertEquals(
             [
                 $archivedxID => $archivedxID
@@ -162,7 +162,7 @@ public function testBatchRestore()
         $this->assertEquals(0, $list->last()->ParentID); // archived (parent)
 
         // Run restore
-        $result = json_decode($action->run($list), true);
+        $result = json_decode($action->run($list) ?? '', true);
         $this->assertEquals(
             [
                 // Order of archived is opposite to order items are passed in, as
diff --git a/tests/php/Controllers/CMSMainTest.php b/tests/php/Controllers/CMSMainTest.php
index 6584f0b8d8..f61158f427 100644
--- a/tests/php/Controllers/CMSMainTest.php
+++ b/tests/php/Controllers/CMSMainTest.php
@@ -56,8 +56,8 @@ public function testSiteTreeHints()
         $rawHints = singleton(CMSMain::class)->SiteTreeHints();
         $this->assertNotNull($rawHints);
 
-        $rawHints = preg_replace('/^"(.*)"$/', '$1', Convert::xml2raw($rawHints));
-        $hints = json_decode($rawHints, true);
+        $rawHints = preg_replace('/^"(.*)"$/', '$1', Convert::xml2raw($rawHints) ?? '');
+        $hints = json_decode($rawHints ?? '', true);
 
         $this->assertArrayHasKey('Root', $hints);
         $this->assertArrayHasKey('Page', $hints);
@@ -100,7 +100,7 @@ public function testChildFilter()
 
         // Check query
         $response = $this->get('admin/pages/childfilter?ParentID=' . $pageA->ID);
-        $children = json_decode($response->getBody());
+        $children = json_decode($response->getBody() ?? '');
         $this->assertFalse($response->isError());
 
         // Page A can't have unrelated children
@@ -137,7 +137,7 @@ public function testPublish()
         $actions = CMSBatchActionHandler::config()->batch_actions;
         if (isset($actions['publish'])) {
             $response = $this->get('admin/pages/batchactions/publish?ajax=1&csvIDs=' . implode(',', [$page1->ID, $page2->ID]));
-            $responseData = json_decode($response->getBody(), true);
+            $responseData = json_decode($response->getBody() ?? '', true);
             $this->assertArrayHasKey($page1->ID, $responseData['modified']);
             $this->assertArrayHasKey($page2->ID, $responseData['modified']);
         }
@@ -335,7 +335,7 @@ public function testCreationOfRestrictedPage()
             ]
         );
         $this->assertFalse($response->isError());
-        $ok = preg_match('/edit\/show\/(\d*)/', $response->getHeader('X-ControllerURL'), $matches);
+        $ok = preg_match('/edit\/show\/(\d*)/', $response->getHeader('X-ControllerURL') ?? '', $matches);
         $this->assertNotEmpty($ok);
         $newPageId = $matches[1];
 
@@ -360,7 +360,7 @@ public function testCreationOfRestrictedPage()
         // Verify that the page was created and redirected to accurately
         $newerPage = SiteTree::get()->byID($newPageId)->AllChildren()->first();
         $this->assertNotEmpty($newerPage);
-        $ok = preg_match('/edit\/show\/(\d*)/', $response->getHeader('X-ControllerURL'), $matches);
+        $ok = preg_match('/edit\/show\/(\d*)/', $response->getHeader('X-ControllerURL') ?? '', $matches);
         $this->assertNotEmpty($ok);
         $newerPageID = $matches[1];
         $this->assertEquals($newerPage->ID, $newerPageID);
@@ -398,7 +398,7 @@ public function testBreadcrumbs()
         $crumbs = $parser->getBySelector('.breadcrumbs-wrapper .crumb');
 
         $this->assertNotNull($crumbs);
-        $this->assertEquals(2, count($crumbs));
+        $this->assertEquals(2, count($crumbs ?? []));
         $this->assertEquals('Page 3', (string)$crumbs[0]);
         $this->assertEquals('Page 3.1', (string)$crumbs[1]);
 
diff --git a/tests/php/Controllers/CMSPageHistoryControllerTest.php b/tests/php/Controllers/CMSPageHistoryControllerTest.php
index 18ef6d7a7d..40d564b500 100755
--- a/tests/php/Controllers/CMSPageHistoryControllerTest.php
+++ b/tests/php/Controllers/CMSPageHistoryControllerTest.php
@@ -112,7 +112,7 @@ public function testVersionsForm()
 
         $form = $this->cssParser()->getBySelector('#Form_VersionsForm');
 
-        $this->assertEquals(1, count($form));
+        $this->assertEquals(1, count($form ?? []));
 
         // check the page ID is present
         $hidden = $form[0]->xpath("fieldset/input[@type='hidden']");
@@ -122,7 +122,7 @@ public function testVersionsForm()
 
         // ensure that all the versions are present in the table and displayed
         $rows = $form[0]->xpath("fieldset/table/tbody/tr");
-        $this->assertEquals(4, count($rows));
+        $this->assertEquals(4, count($rows ?? []));
     }
 
     public function testVersionsFormTableContainsInformation()
diff --git a/tests/php/Controllers/CMSSiteTreeFilterTest.php b/tests/php/Controllers/CMSSiteTreeFilterTest.php
index 9946894f1f..b76688f252 100644
--- a/tests/php/Controllers/CMSSiteTreeFilterTest.php
+++ b/tests/php/Controllers/CMSSiteTreeFilterTest.php
@@ -40,7 +40,7 @@ public function testSearchFilterByTitle()
 
         $this->assertTrue($f->isPageIncluded($page1));
         $this->assertFalse($f->isPageIncluded($page2));
-        $this->assertEquals(1, count($results));
+        $this->assertEquals(1, count($results ?? []));
         $this->assertEquals(
             ['ID' => $page1->ID, 'ParentID' => 0],
             $results[0]
@@ -68,7 +68,7 @@ public function testIncludesParentsForNestedMatches()
 
         $this->assertTrue($f->isPageIncluded($parent));
         $this->assertTrue($f->isPageIncluded($child));
-        $this->assertEquals(1, count($results));
+        $this->assertEquals(1, count($results ?? []));
         $this->assertEquals(
             ['ID' => $child->ID, 'ParentID' => $parent->ID],
             $results[0]
@@ -95,7 +95,7 @@ public function testChangedPagesFilter()
 
         $this->assertTrue($f->isPageIncluded($changedPage));
         $this->assertFalse($f->isPageIncluded($unchangedPage));
-        $this->assertEquals(1, count($results));
+        $this->assertEquals(1, count($results ?? []));
         $this->assertEquals(
             ['ID' => $changedPage->ID, 'ParentID' => 0],
             $results[0]
@@ -104,7 +104,7 @@ public function testChangedPagesFilter()
         // Check that only changed pages are returned
         $f = new CMSSiteTreeFilter_ChangedPages(['Term' => 'No Matches']);
         $results = $f->pagesIncluded();
-        $this->assertEquals(0, count($results));
+        $this->assertEquals(0, count($results ?? []));
 
         // If we roll back to an earlier version than what's on the published site, we should still show the changed
         $changedPage->Title = 'Changed 2';
@@ -115,7 +115,7 @@ public function testChangedPagesFilter()
         $f = new CMSSiteTreeFilter_ChangedPages(['Term' => 'Changed']);
         $results = $f->pagesIncluded();
 
-        $this->assertEquals(1, count($results));
+        $this->assertEquals(1, count($results ?? []));
         $this->assertEquals(['ID' => $changedPage->ID, 'ParentID' => 0], $results[0]);
     }
 
@@ -166,7 +166,7 @@ public function testDateFromToLastSameDate()
     {
         $draftPage = $this->objFromFixture('Page', 'page4');
         // Grab the date
-        $date = substr($draftPage->LastEdited, 0, 10);
+        $date = substr($draftPage->LastEdited ?? '', 0, 10);
         // Filter with that date
         $filter = new CMSSiteTreeFilter_Search([
             'LastEditedFrom' => $date,
diff --git a/tests/php/Controllers/CMSTreeTest.php b/tests/php/Controllers/CMSTreeTest.php
index f4743c8376..c17b75cd33 100644
--- a/tests/php/Controllers/CMSTreeTest.php
+++ b/tests/php/Controllers/CMSTreeTest.php
@@ -98,7 +98,7 @@ public function testUpdateTreeNodes()
         $result = $this->get('admin/pages/edit/updatetreenodes?ids='.$page1->ID);
         $this->assertEquals(200, $result->getStatusCode());
         $this->assertEquals('application/json', $result->getHeader('Content-Type'));
-        $data = json_decode($result->getBody(), true);
+        $data = json_decode($result->getBody() ?? '', true);
         $pageData = $data[$page1->ID];
         $this->assertEquals(0, $pageData['ParentID']);
         $this->assertEquals($page2->ID, $pageData['NextID']);
@@ -108,7 +108,7 @@ public function testUpdateTreeNodes()
         $result = $this->get('admin/pages/edit/updatetreenodes?ids='.$page31->ID);
         $this->assertEquals(200, $result->getStatusCode());
         $this->assertEquals('application/json', $result->getHeader('Content-Type'));
-        $data = json_decode($result->getBody(), true);
+        $data = json_decode($result->getBody() ?? '', true);
         $pageData = $data[$page31->ID];
         $this->assertEquals($page3->ID, $pageData['ParentID']);
         $this->assertEquals($page32->ID, $pageData['NextID']);
@@ -118,14 +118,14 @@ public function testUpdateTreeNodes()
         $result = $this->get('admin/pages/edit/updatetreenodes?ids='.$page1->ID.','.$page2->ID);
         $this->assertEquals(200, $result->getStatusCode());
         $this->assertEquals('application/json', $result->getHeader('Content-Type'));
-        $data = json_decode($result->getBody(), true);
-        $this->assertEquals(2, count($data));
+        $data = json_decode($result->getBody() ?? '', true);
+        $this->assertEquals(2, count($data ?? []));
 
         // Invalid IDs
         $result = $this->get('admin/pages/edit/updatetreenodes?ids=-3');
         $this->assertEquals(200, $result->getStatusCode());
         $this->assertEquals('application/json', $result->getHeader('Content-Type'));
-        $data = json_decode($result->getBody(), true);
-        $this->assertEquals(0, count($data));
+        $data = json_decode($result->getBody() ?? '', true);
+        $this->assertEquals(0, count($data ?? []));
     }
 }
diff --git a/tests/php/Controllers/ContentControllerTest.php b/tests/php/Controllers/ContentControllerTest.php
index b094c9d90a..e6acd9b5a8 100755
--- a/tests/php/Controllers/ContentControllerTest.php
+++ b/tests/php/Controllers/ContentControllerTest.php
@@ -172,7 +172,7 @@ public function testGetViewer()
             $page->copyVersionToStage(Versioned::DRAFT, Versioned::LIVE);
 
             $response = $this->get($page->RelativeLink());
-            $this->assertEquals("ContentControllerTestPageWithoutController", trim($response->getBody()));
+            $this->assertEquals("ContentControllerTestPageWithoutController", trim($response->getBody() ?? ''));
 
             // // This should fall over to user Page.ss
             $page = new ContentControllerTestPage();
@@ -181,7 +181,7 @@ public function testGetViewer()
             $page->copyVersionToStage(Versioned::DRAFT, Versioned::LIVE);
 
             $response = $this->get($page->RelativeLink());
-            $this->assertEquals("Page", trim($response->getBody()));
+            $this->assertEquals("Page", trim($response->getBody() ?? ''));
 
 
             // Test that the action template is rendered.
@@ -191,12 +191,12 @@ public function testGetViewer()
             $page->copyVersionToStage(Versioned::DRAFT, Versioned::LIVE);
 
             $response = $this->get($page->RelativeLink("test"));
-            $this->assertEquals("ContentControllerTestPage_test", trim($response->getBody()));
+            $this->assertEquals("ContentControllerTestPage_test", trim($response->getBody() ?? ''));
 
             // Test that an action without a template will default to the index template, which is
             // to say the default Page.ss template
             $response = $this->get($page->RelativeLink("testwithouttemplate"));
-            $this->assertEquals("Page", trim($response->getBody()));
+            $this->assertEquals("Page", trim($response->getBody() ?? ''));
 
             // Test that an action with a template will render the both action template *and* the
             // correct parent template
diff --git a/tests/php/Controllers/SilverStripeNavigatorTest.php b/tests/php/Controllers/SilverStripeNavigatorTest.php
index bfb3f7eece..18fd5832e6 100644
--- a/tests/php/Controllers/SilverStripeNavigatorTest.php
+++ b/tests/php/Controllers/SilverStripeNavigatorTest.php
@@ -23,7 +23,7 @@ public function testGetItems()
         $navigator = new SilverStripeNavigator($page);
 
         $items = $navigator->getItems();
-        $classes = array_map('get_class', $items->toArray());
+        $classes = array_map('get_class', $items->toArray() ?? []);
         $this->assertContains(
             SilverStripeNavigatorItem_StageLink::class,
             $classes,
@@ -48,18 +48,18 @@ public function testCanView()
         // TODO Shouldn't be necessary but SapphireTest logs in as ADMIN by default
         $this->logInWithPermission('CMS_ACCESS_CMSMain');
         $items = $navigator->getItems();
-        $classes = array_map('get_class', $items->toArray());
+        $classes = array_map('get_class', $items->toArray() ?? []);
         $this->assertNotContains(SilverStripeNavigatorTest_ProtectedTestItem::class, $classes);
 
         $this->logInWithPermission('ADMIN');
         $items = $navigator->getItems();
-        $classes = array_map('get_class', $items->toArray());
+        $classes = array_map('get_class', $items->toArray() ?? []);
         $this->assertContains(SilverStripeNavigatorTest_ProtectedTestItem::class, $classes);
 
         // Unversioned record shouldn't be viewable in stage / live specific views
         $unversioned = new SilverStripeNavigatorTest\UnstagedRecord();
         $navigator2 = new SilverStripeNavigator($unversioned);
-        $classes = array_map('get_class', $navigator2->getItems()->toArray());
+        $classes = array_map('get_class', $navigator2->getItems()->toArray() ?? []);
         $this->assertNotContains(SilverStripeNavigatorItem_LiveLink::class, $classes);
         $this->assertNotContains(SilverStripeNavigatorItem_StageLink::class, $classes);
         $this->assertNotContains(SilverStripeNavigatorItem_ArchiveLink::class, $classes);
diff --git a/tests/php/GraphQL/LinkablePluginTest.php b/tests/php/GraphQL/LinkablePluginTest.php
index 6c832ec460..2687a39337 100644
--- a/tests/php/GraphQL/LinkablePluginTest.php
+++ b/tests/php/GraphQL/LinkablePluginTest.php
@@ -78,8 +78,8 @@ public function testResolver()
         $this->assertTrue($result->exists());
         $this->assertCount(2, $result);
         $titles = $result->column('Title');
-        $this->assertTrue(in_array('Test page', $titles));
-        $this->assertTrue(in_array('Other test page', $titles));
+        $this->assertTrue(in_array('Test page', $titles ?? []));
+        $this->assertTrue(in_array('Other test page', $titles ?? []));
 
         $result = LinkablePlugin::applyLinkFilter(
             'test',
diff --git a/tests/php/Model/SiteTreeBacklinksTest.php b/tests/php/Model/SiteTreeBacklinksTest.php
index dc0a285150..927586db48 100644
--- a/tests/php/Model/SiteTreeBacklinksTest.php
+++ b/tests/php/Model/SiteTreeBacklinksTest.php
@@ -37,8 +37,8 @@ protected function setUp(): void
         $page3 = $this->objFromFixture('Page', 'page3');
         $page3->Content = str_replace(
             '$page1.ID',
-            $this->objFromFixture('Page', 'page1')->ID,
-            $page3->Content
+            $this->objFromFixture('Page', 'page1')->ID ?? '',
+            $page3->Content ?? ''
         );
         $page3->write();
     }
diff --git a/tests/php/Model/SiteTreeHTMLEditorFieldTest.php b/tests/php/Model/SiteTreeHTMLEditorFieldTest.php
index a3daa927d6..d2324b45b1 100644
--- a/tests/php/Model/SiteTreeHTMLEditorFieldTest.php
+++ b/tests/php/Model/SiteTreeHTMLEditorFieldTest.php
@@ -26,8 +26,8 @@ protected function setUp(): void
         $files = File::get()->exclude('ClassName', Folder::class);
         foreach ($files as $file) {
             $destPath = TestAssetStore::getLocalPath($file);
-            Filesystem::makeFolder(dirname($destPath));
-            file_put_contents($destPath, str_repeat('x', 1000000));
+            Filesystem::makeFolder(dirname($destPath ?? ''));
+            file_put_contents($destPath ?? '', str_repeat('x', 1000000));
         }
 
         // Ensure all pages are published
diff --git a/tests/php/Model/SiteTreeLinkTrackingTest.php b/tests/php/Model/SiteTreeLinkTrackingTest.php
index 5d0c50c81c..4247eee184 100644
--- a/tests/php/Model/SiteTreeLinkTrackingTest.php
+++ b/tests/php/Model/SiteTreeLinkTrackingTest.php
@@ -81,11 +81,11 @@ protected function highlight($content)
     public function testHighlighter()
     {
         $content = $this->highlight('<a href="[sitetree_link,id=123]" class="existing-class">link</a>');
-        $this->assertEquals(substr_count($content, 'ss-broken'), 1, 'A ss-broken class is added to the broken link.');
-        $this->assertEquals(substr_count($content, 'existing-class'), 1, 'Existing class is not removed.');
+        $this->assertEquals(substr_count($content ?? '', 'ss-broken'), 1, 'A ss-broken class is added to the broken link.');
+        $this->assertEquals(substr_count($content ?? '', 'existing-class'), 1, 'Existing class is not removed.');
 
         $content = $this->highlight('<a href="[sitetree_link,id=123]">link</a>');
-        $this->assertEquals(substr_count($content, 'ss-broken'), 1, 'ss-broken class is added to the broken link.');
+        $this->assertEquals(substr_count($content ?? '', 'ss-broken'), 1, 'ss-broken class is added to the broken link.');
 
         $otherPage = new Page();
         $otherPage->Content = '';
@@ -94,7 +94,7 @@ public function testHighlighter()
         $content = $this->highlight(
             "<a href=\"[sitetree_link,id=$otherPage->ID]\" class=\"existing-class ss-broken ss-broken\">link</a>"
         );
-        $this->assertEquals(substr_count($content, 'ss-broken'), 0, 'All ss-broken classes are removed from good link');
-        $this->assertEquals(substr_count($content, 'existing-class'), 1, 'Existing class is not removed.');
+        $this->assertEquals(substr_count($content ?? '', 'ss-broken'), 0, 'All ss-broken classes are removed from good link');
+        $this->assertEquals(substr_count($content ?? '', 'existing-class'), 1, 'Existing class is not removed.');
     }
 }
diff --git a/tests/php/Model/SiteTreeTest.php b/tests/php/Model/SiteTreeTest.php
index f801b7a532..0728ba4a14 100644
--- a/tests/php/Model/SiteTreeTest.php
+++ b/tests/php/Model/SiteTreeTest.php
@@ -146,7 +146,7 @@ public function testDisallowedURLGeneration($title, $urlSegment)
     public function testDisallowedChildURLGeneration($title, $urlSegment)
     {
         // Using the same dataprovider, strip out the -2 from the admin and dev segment
-        $urlSegment = str_replace('-2', '', $urlSegment);
+        $urlSegment = str_replace('-2', '', $urlSegment ?? '');
         $page = Page::create(['Title' => $title, 'ParentID' => 1]);
         $id = $page->write();
         $page = Page::get()->byID($id);
@@ -821,9 +821,9 @@ public function testCompareVersions()
 
         $diff = $page->compareVersions(1, 2);
 
-        $processedContent = trim($diff->Content);
-        $processedContent = preg_replace('/\s*</', '<', $processedContent);
-        $processedContent = preg_replace('/>\s*/', '>', $processedContent);
+        $processedContent = trim($diff->Content ?? '');
+        $processedContent = preg_replace('/\s*</', '<', $processedContent ?? '');
+        $processedContent = preg_replace('/>\s*/', '>', $processedContent ?? '');
         $this->assertEquals("<ins><span>This is a test</span></ins>", $processedContent);
 
         Diff::$html_cleaner_class = $oldCleanerClass;
@@ -1485,7 +1485,7 @@ public function testMetaComponents()
         // test the meta generator tag version can be configured off
         Config::modify()->set(SiteTree::class, 'show_meta_generator_version', false);
         $content = $expected['generator']['attributes']['content'];
-        $expected['generator']['attributes']['content'] = str_replace(' 4.50', '', $content);
+        $expected['generator']['attributes']['content'] = str_replace(' 4.50', '', $content ?? '');
         $this->assertEquals($expected, $page->MetaComponents());
     }
 
diff --git a/tests/php/Model/VirtualPageTest_TestDBField.php b/tests/php/Model/VirtualPageTest_TestDBField.php
index f9f602225f..5554567ff3 100644
--- a/tests/php/Model/VirtualPageTest_TestDBField.php
+++ b/tests/php/Model/VirtualPageTest_TestDBField.php
@@ -9,6 +9,6 @@ class VirtualPageTest_TestDBField extends DBVarchar implements TestOnly
 {
     public function forTemplate()
     {
-        return strtoupper($this->XML());
+        return strtoupper($this->XML() ?? '');
     }
 }
diff --git a/tests/php/Reports/CmsReportsTest.php b/tests/php/Reports/CmsReportsTest.php
index 6132eb3089..ffb8fdaaaa 100644
--- a/tests/php/Reports/CmsReportsTest.php
+++ b/tests/php/Reports/CmsReportsTest.php
@@ -52,12 +52,12 @@ public function isReportBroken($report, $isDraftBroken, $isPublishedBroken)
 
         // ASSERT that the "draft" report is returning the correct results.
         $parameters = ['CheckSite' => 'Draft'];
-        $results = count($report->sourceRecords($parameters, null, null)) > 0;
+        $results = count($report->sourceRecords($parameters, null, null) ?? []) > 0;
         $isDraftBroken ? $this->assertTrue($results, "{$class} has NOT returned the correct DRAFT results, as NO pages were found.") : $this->assertFalse($results, "{$class} has NOT returned the correct DRAFT results, as pages were found.");
 
         // ASSERT that the "published" report is returning the correct results.
         $parameters = ['CheckSite' => 'Published', 'OnLive' => 1];
-        $results = count($report->sourceRecords($parameters, null, null)) > 0;
+        $results = count($report->sourceRecords($parameters, null, null) ?? []) > 0;
         $isPublishedBroken ? $this->assertTrue($results, "{$class} has NOT returned the correct PUBLISHED results, as NO pages were found.") : $this->assertFalse($results, "{$class} has NOT returned the correct PUBLISHED results, as pages were found.");
     }
 
@@ -124,7 +124,7 @@ public function testBrokenLinks()
 
         // Correct the "draft" broken link.
 
-        $page->Content = str_replace('987654321', $page->ID, $page->Content);
+        $page->Content = str_replace('987654321', $page->ID ?? '', $page->Content ?? '');
         $page->writeToStage('Stage');
 
         // ASSERT that the "draft" report has NOT detected the page having a broken link.
@@ -191,7 +191,7 @@ public function testBrokenFiles()
         $file = File::create();
         $file->Filename = 'name.pdf';
         $file->write();
-        $page->Content = str_replace('987654321', $file->ID, $page->Content);
+        $page->Content = str_replace('987654321', $file->ID ?? '', $page->Content ?? '');
         $page->writeToStage('Stage');
 
         // ASSERT that the "draft" report has NOT detected the page having a broken file.
diff --git a/tests/php/Search/CMSMainSearchFormTest.php b/tests/php/Search/CMSMainSearchFormTest.php
index a59ad26a0f..9835552a43 100644
--- a/tests/php/Search/CMSMainSearchFormTest.php
+++ b/tests/php/Search/CMSMainSearchFormTest.php
@@ -25,7 +25,7 @@ public function testTitleFilter()
         );
 
         $titles = $this->getPageTitles();
-        $this->assertEquals(count($titles), 1);
+        $this->assertEquals(count($titles ?? []), 1);
         // For some reason the title gets split into two lines
 
         $this->assertStringContainsString('Page 1', $titles[0]);
@@ -37,7 +37,7 @@ protected function getPageTitles()
         $links = $this->cssParser()->getBySelector('.col-getTreeTitle span.item');
         if ($links) {
             foreach ($links as $link) {
-                $titles[] = preg_replace('/\n/', ' ', $link->asXML());
+                $titles[] = preg_replace('/\n/', ' ', $link->asXML() ?? '');
             }
         }
         return $titles;
diff --git a/tests/php/Tasks/MigrateSiteTreeLinkingTaskTest.php b/tests/php/Tasks/MigrateSiteTreeLinkingTaskTest.php
index 1181d268c1..12f92ccdc7 100644
--- a/tests/php/Tasks/MigrateSiteTreeLinkingTaskTest.php
+++ b/tests/php/Tasks/MigrateSiteTreeLinkingTaskTest.php
@@ -46,7 +46,7 @@ protected function setUp(): void
         ];
         foreach (DB::query('SELECT "ID", "Content" FROM "SiteTree"') as $row) {
             $id = (int)$row['ID'];
-            $content = str_replace(array_keys($replacements), array_values($replacements), $row['Content']);
+            $content = str_replace(array_keys($replacements ?? []), array_values($replacements ?? []), $row['Content'] ?? '');
             DB::prepared_query('UPDATE "SiteTree" SET "Content" = ? WHERE "ID" = ?', [$content, $id]);
         }
         DataObject::reset();