diff --git a/src/Control/LocaleAdmin.php b/src/Control/LocaleAdmin.php
index 152923a1..87a358a9 100644
--- a/src/Control/LocaleAdmin.php
+++ b/src/Control/LocaleAdmin.php
@@ -44,7 +44,7 @@ public function getClientConfig()
                             'code' => $locale->getLocale(),
                             'title' => $locale->getTitle(),
                         ];
-                    }, Locale::getCached()->toArray()),
+                    }, Locale::getCached()->toArray() ?? []),
                     'locale' => FluentState::singleton()->getLocale(),
                     'param' => FluentDirectorExtension::config()->get('query_param'),
                 ]
diff --git a/src/Extension/FluentDirectorExtension.php b/src/Extension/FluentDirectorExtension.php
index 6ebf1d66..adb480f8 100644
--- a/src/Extension/FluentDirectorExtension.php
+++ b/src/Extension/FluentDirectorExtension.php
@@ -123,7 +123,7 @@ protected function getExplicitRoutes($originalRules)
             $url = $localeObj->getURLSegment();
 
             // apply encode so we could route urls that contain multi-byte charaters
-            $url = urlencode($url);
+            $url = urlencode($url ?? '');
 
             // Apply to nested page url
             $controller = $this->getRuleController($originalRules['$URLSegment//$Action/$ID/$OtherID'], $localeObj);
@@ -166,9 +166,9 @@ protected function getRuleController($existingRule, $localeObj)
      */
     protected function insertRuleBefore(array $rules, $key, array $rule, $prependIfMissing = true)
     {
-        $i = array_search($key, array_keys($rules));
+        $i = array_search($key, array_keys($rules ?? []));
         if ($i !== false) {
-            return array_slice($rules, 0, $i, true) + $rule + array_slice($rules, $i, null, true);
+            return array_slice($rules ?? [], 0, $i, true) + $rule + array_slice($rules ?? [], $i ?? 0, null, true);
         } elseif ($prependIfMissing) {
             $rules = $rule + $rules;
         }
diff --git a/src/Extension/FluentExtension.php b/src/Extension/FluentExtension.php
index 07ff148f..86d205dc 100644
--- a/src/Extension/FluentExtension.php
+++ b/src/Extension/FluentExtension.php
@@ -199,7 +199,7 @@ protected function isFieldLocalised($field, $type, $class)
             return false;
         }
         if ($filter && is_array($filter)) {
-            return in_array($field, $filter);
+            return in_array($field, $filter ?? []);
         }
 
         // Named blacklist
@@ -249,7 +249,7 @@ public function getLocalisedTables()
 
             // Mark this table as translatable
             $table = DataObject::getSchema()->tableName($class);
-            $includedTables[$table] = array_keys($translatedFields);
+            $includedTables[$table] = array_keys($translatedFields ?? []);
         }
         return $includedTables;
     }
@@ -265,11 +265,11 @@ public function getLocalisedTables()
     protected function anyMatch($value, $patterns)
     {
         // Test both explicit value, as well as the value stripped of any trailing parameters
-        $valueBase = preg_replace('/\(.*/', '', $value);
+        $valueBase = preg_replace('/\(.*/', '', $value ?? '');
         foreach ($patterns as $pattern) {
-            if (strpos($pattern, '/') === 0) {
+            if (strpos($pattern ?? '', '/') === 0) {
                 // Assume value prefaced with '/' are regexp
-                if (preg_match($pattern, $value) || preg_match($pattern, $valueBase)) {
+                if (preg_match($pattern ?? '', $value ?? '') || preg_match($pattern ?? '', $valueBase ?? '')) {
                     return true;
                 }
             } else {
@@ -352,7 +352,7 @@ protected function validateChildConfig()
                 'extensions',
                 Config::EXCLUDE_EXTRA_SOURCES | Config::UNINHERITED
             ) ?: [];
-        $extensions = array_filter(array_values($extensions));
+        $extensions = array_filter(array_values($extensions ?? []));
         foreach ($extensions as $extension) {
             $extensionClass = Extension::get_classname_without_arguments($extension);
             if (is_a($extensionClass, self::class, true)) {
@@ -460,11 +460,11 @@ public function augmentSQL(SQLSelect $query, DataQuery $dataQuery = null)
                     $localisedColumn = str_replace(
                         "\"{$field}\"",
                         "\"{$table}\".\"{$field}\"",
-                        $localisedColumn
+                        $localisedColumn ?? ''
                     );
                 }
                 // Apply substitutions
-                $localisedColumn = str_replace($conditionSearch, $conditionReplace, $localisedColumn);
+                $localisedColumn = str_replace($conditionSearch ?? '', $conditionReplace ?? '', $localisedColumn ?? '');
                 if ($column !== $localisedColumn) {
                     // Wrap sort in group to prevent dataquery messing it up
                     unset($order[$column]);
@@ -488,12 +488,12 @@ public function augmentSQL(SQLSelect $query, DataQuery $dataQuery = null)
                 $parameters = array();
                 $predicate = $condition->conditionSQL($parameters);
             } else {
-                $parameters = array_values(reset($condition));
-                $predicate = key($condition);
+                $parameters = array_values(reset($condition) ?? []);
+                $predicate = key($condition ?? []);
             }
 
             // Apply substitutions
-            $localisedPredicate = str_replace($conditionSearch, $conditionReplace, $predicate);
+            $localisedPredicate = str_replace($conditionSearch ?? '', $conditionReplace ?? '', $predicate ?? '');
 
             $where[$index] = [
                 $localisedPredicate => $parameters
@@ -581,8 +581,8 @@ protected function localiseManipulationTable(&$manipulation, $table, $localeTabl
 
         // Filter fields by localised fields
         $localisedUpdate['fields'] = array_intersect_key(
-            $updates['fields'],
-            array_combine($localisedFields, $localisedFields)
+            $updates['fields'] ?? [],
+            array_combine($localisedFields ?? [], $localisedFields ?? [])
         );
         unset($localisedUpdate['fields']['id']);
 
@@ -938,7 +938,7 @@ public function updateCMSFields(FieldList $fields)
                 // If the translated field has an ID suffix also check for the non-suffixed version
                 // E.g. UploadField()
                 $field = $fields->dataFieldByName($translatedField);
-                if (!$field && preg_match('/^(?<field>\w+)ID$/', $translatedField, $matches)) {
+                if (!$field && preg_match('/^(?<field>\w+)ID$/', $translatedField ?? '', $matches)) {
                     $field = $fields->dataFieldByName($matches['field']);
                 }
                 if (!$field || $field->hasClass('fluent__localised-field')) {
@@ -985,24 +985,24 @@ protected function requireSavedInLocale()
     protected function detectLocalisedTableField($tables, $sql)
     {
         // Check explicit "table"."field" within the fragment
-        if (preg_match('/"(?<table>[\w\\\\]+)"\."(?<field>\w+)"/i', $sql, $matches)) {
+        if (preg_match('/"(?<table>[\w\\\\]+)"\."(?<field>\w+)"/i', $sql ?? '', $matches)) {
             $table = $matches['table'];
             $field = $matches['field'];
 
             // Ensure both table and this field are valid
-            if (empty($tables[$table]) || !in_array($field, $tables[$table])) {
+            if (empty($tables[$table]) || !in_array($field, $tables[$table] ?? [])) {
                 return [null, null, false];
             }
             return [$table, $field, true];
         }
 
         // Check sole "field" without table specifier ("name" without leading or trailing '.')
-        if (preg_match('/(?<![.])"(?<field>\w+)"(?![.])/i', $sql, $matches)) {
+        if (preg_match('/(?<![.])"(?<field>\w+)"(?![.])/i', $sql ?? '', $matches)) {
             $field = $matches['field'];
 
             // Check if this field is in any of the tables, and just pick any that match
             foreach ($tables as $table => $fields) {
-                if (in_array($field, $fields)) {
+                if (in_array($field, $fields ?? [])) {
                     return [$table, $field, false];
                 }
             }
diff --git a/src/Extension/FluentFilteredExtension.php b/src/Extension/FluentFilteredExtension.php
index f074e2dc..dabbd3e8 100644
--- a/src/Extension/FluentFilteredExtension.php
+++ b/src/Extension/FluentFilteredExtension.php
@@ -167,10 +167,10 @@ protected function getModeIsStage()
         $readingMode = Versioned::get_reading_mode();
         $draft = Versioned::DRAFT;
 
-        if (strlen($readingMode) === 0) {
+        if (strlen($readingMode ?? '') === 0) {
             $readingMode = Versioned::DEFAULT_MODE;
         }
 
-        return substr_compare($readingMode, $draft, strlen($readingMode) - strlen($draft), strlen($draft)) === 0;
+        return substr_compare($readingMode ?? '', $draft ?? '', strlen($readingMode ?? '') - strlen($draft ?? ''), strlen($draft ?? '')) === 0;
     }
 }
diff --git a/src/Extension/FluentSiteTreeExtension.php b/src/Extension/FluentSiteTreeExtension.php
index 2fabca6f..e87c7a89 100644
--- a/src/Extension/FluentSiteTreeExtension.php
+++ b/src/Extension/FluentSiteTreeExtension.php
@@ -61,7 +61,7 @@ public function updateRelativeLink(&$base, &$action)
         if (!$this->owner->exists()) {
             $base = Controller::join_links(
                 $base,
-                '?' . FluentDirectorExtension::config()->get('query_param') . '=' . urlencode($localeObj->Locale)
+                '?' . FluentDirectorExtension::config()->get('query_param') . '=' . urlencode($localeObj->Locale ?? '')
             );
             return;
         }
diff --git a/src/Extension/FluentVersionedExtension.php b/src/Extension/FluentVersionedExtension.php
index a9f436bb..f4b71153 100644
--- a/src/Extension/FluentVersionedExtension.php
+++ b/src/Extension/FluentVersionedExtension.php
@@ -231,7 +231,7 @@ public function augmentWrite(&$manipulation)
                 if ($suffix === self::SUFFIX_VERSIONS) {
                     $localisedVersionFields = array_merge(
                         $localisedVersionFields,
-                        array_keys($this->defaultVersionsFields)
+                        array_keys($this->defaultVersionsFields ?? [])
                     );
                 }
 
@@ -428,7 +428,7 @@ public static function prepoulateIdsInLocale($locale, $dataObjectClass, $populat
             $ids = $result->column('RecordID');
 
             // We need to execute ourselves as the param is lost from the subSelect
-            self::$idsInLocaleCache[$locale][$table] = array_combine($ids, $ids);
+            self::$idsInLocaleCache[$locale][$table] = array_combine($ids ?? [], $ids ?? []);
             self::$idsInLocaleCache[$locale][$table]['_complete'] = true;
         }
     }
diff --git a/src/Middleware/InitStateMiddleware.php b/src/Middleware/InitStateMiddleware.php
index f29bea61..c0cb38f6 100644
--- a/src/Middleware/InitStateMiddleware.php
+++ b/src/Middleware/InitStateMiddleware.php
@@ -63,10 +63,10 @@ public function getIsFrontend(HTTPRequest $request)
     {
         $adminPaths = static::config()->get('admin_url_paths');
         $adminPaths[] = AdminRootController::config()->get('url_base') . '/';
-        $currentPath = rtrim($request->getURL(), '/') . '/';
+        $currentPath = rtrim($request->getURL() ?? '', '/') . '/';
 
         foreach ($adminPaths as $adminPath) {
-            if (substr($currentPath, 0, strlen($adminPath)) === $adminPath) {
+            if (substr($currentPath ?? '', 0, strlen($adminPath ?? '')) === $adminPath) {
                 return false;
             }
         }
diff --git a/src/Model/CachableModel.php b/src/Model/CachableModel.php
index 9ee835dc..fe29576c 100644
--- a/src/Model/CachableModel.php
+++ b/src/Model/CachableModel.php
@@ -84,7 +84,7 @@ protected static function databaseIsReady()
         }
 
         $objFields = $object->getSchema()->databaseFields($object, false);
-        $missingFields = array_diff_key($objFields, $dbFields);
+        $missingFields = array_diff_key($objFields ?? [], $dbFields);
 
         if ($missingFields) {
             return false;
diff --git a/src/Model/Locale.php b/src/Model/Locale.php
index 0c9cd244..643ffa2d 100644
--- a/src/Model/Locale.php
+++ b/src/Model/Locale.php
@@ -153,7 +153,7 @@ public function getDefaultLocale()
      */
     public function getLocaleSuffix()
     {
-        $bits = explode('_', $this->Locale);
+        $bits = explode('_', $this->Locale ?? '');
         return array_pop($bits);
     }
 
@@ -350,7 +350,7 @@ public static function getByLocale($locale)
      */
     public function isLocale($locale)
     {
-        return stripos(i18n::convert_rfc1766($locale), i18n::convert_rfc1766($this->Locale)) === 0;
+        return stripos(i18n::convert_rfc1766($locale) ?? '', i18n::convert_rfc1766($this->Locale) ?? '') === 0;
     }
 
     /**
diff --git a/src/Search/FluentSearchForm.php b/src/Search/FluentSearchForm.php
index bd697345..7c59a7b2 100644
--- a/src/Search/FluentSearchForm.php
+++ b/src/Search/FluentSearchForm.php
@@ -51,9 +51,9 @@ public function getResults()
         ];
         foreach ($keyword_patterns as $k_p) {
             $keywords = preg_replace_callback(
-                $k_p['patterns'],
+                $k_p['patterns'] ?? '',
                 $k_p['callback'],
-                $keywords
+                $keywords ?? ''
             );
         }
 
@@ -70,10 +70,10 @@ public function getResults()
             ORDER BY Relevance DESC
 SQL;
         $params = [
-            str_replace(['*', '+', '-'], '', $keywords),
+            str_replace(['*', '+', '-'], '', $keywords ?? ''),
             $current_locale,
             $keywords,
-            htmlentities($keywords, ENT_NOQUOTES, 'UTF-8')
+            htmlentities($keywords ?? '', ENT_NOQUOTES, 'UTF-8')
         ];
         // Generate results list
         $sitetree_objects = SiteTree::get()
diff --git a/src/State/BrowserLocaleDetector.php b/src/State/BrowserLocaleDetector.php
index 06aa32af..b5e440ed 100644
--- a/src/State/BrowserLocaleDetector.php
+++ b/src/State/BrowserLocaleDetector.php
@@ -38,14 +38,14 @@ public function detectLocale(HTTPRequest $request)
         // break up string into pieces (languages and q factors)
         preg_match_all(
             '/(?<code>[a-z]{1,8}(-[a-z]{1,8})?)\s*(;\s*q\s*=\s*(?<priority>1|0\.[0-9]+))?/i',
-            $inputLocales,
+            $inputLocales ?? '',
             $parsedLocales
         );
 
         $prioritisedLocales = [];
-        if (count($parsedLocales['code'])) {
+        if (count($parsedLocales['code'] ?? [])) {
             // create a list like "en" => 0.8
-            $parsedLocales = array_combine($parsedLocales['code'], $parsedLocales['priority']);
+            $parsedLocales = array_combine($parsedLocales['code'] ?? [], $parsedLocales['priority'] ?? []);
 
             // Generate nested list of priorities => [locales]
             foreach ($parsedLocales as $locale => $priority) {
diff --git a/src/Task/ConvertTranslatableTask.php b/src/Task/ConvertTranslatableTask.php
index 217ed5d1..cec80a69 100644
--- a/src/Task/ConvertTranslatableTask.php
+++ b/src/Task/ConvertTranslatableTask.php
@@ -80,7 +80,7 @@ public function fluentClasses()
                 }
             }
         }
-        return array_unique($classes);
+        return array_unique($classes ?? []);
     }
 
     public function run($request)
diff --git a/tests/php/Extension/FluentDirectorExtensionTest.php b/tests/php/Extension/FluentDirectorExtensionTest.php
index 424a0bce..982c89d4 100644
--- a/tests/php/Extension/FluentDirectorExtensionTest.php
+++ b/tests/php/Extension/FluentDirectorExtensionTest.php
@@ -94,7 +94,7 @@ protected function setUpRoutes()
         $rules = Director::config()->rules;
 
         // Modify the rule for our test controller to include the locale parameter
-        $i = array_search('admin', array_keys($rules));
+        $i = array_search('admin', array_keys($rules ?? []));
         if ($i !== false) {
             $rule = [
                 'nouvelle-z%C3%A9lande/TestController//$Action/$ID/$OtherID' => [
@@ -103,7 +103,7 @@ protected function setUpRoutes()
                 ]
             ];
 
-            $rules = array_slice($rules, 0, $i, true) + $rule + array_slice($rules, $i, null, true);
+            $rules = array_slice($rules ?? [], 0, $i, true) + $rule + array_slice($rules ?? [], $i ?? 0, null, true);
         } else {
             throw new \Exception('Could not find "admin" url rule');
         }
diff --git a/tests/php/Extension/FluentSiteTreeExtensionTest.php b/tests/php/Extension/FluentSiteTreeExtensionTest.php
index ef91578f..19f7bfc0 100644
--- a/tests/php/Extension/FluentSiteTreeExtensionTest.php
+++ b/tests/php/Extension/FluentSiteTreeExtensionTest.php
@@ -295,7 +295,7 @@ public function testUpdateCMSActionsDrafted()
 
         $this->assertEquals('Saved', $actionSave->Title());
         // The default value changed between SS 4.0 and 4.1 - assert it contains Publish instead of exact matching
-        $this->assertStringContainsString('publish', strtolower($actionPublish->Title()));
+        $this->assertStringContainsString('publish', strtolower($actionPublish->Title() ?? ''));
     }
 
     /**
diff --git a/tests/php/Middleware/Stub/DetectLocaleMiddlewareSpy.php b/tests/php/Middleware/Stub/DetectLocaleMiddlewareSpy.php
index ff00173d..ce52cdd5 100644
--- a/tests/php/Middleware/Stub/DetectLocaleMiddlewareSpy.php
+++ b/tests/php/Middleware/Stub/DetectLocaleMiddlewareSpy.php
@@ -17,7 +17,7 @@ class DetectLocaleMiddlewareSpy extends DetectLocaleMiddleware implements TestOn
 {
     public function __call($method, $arguments)
     {
-        if (method_exists($this, $method)) {
+        if (method_exists($this, $method ?? '')) {
             return $this->$method(...$arguments);
         }
     }