FIX: Fixed issue where a crash could occur when an error page is gene…

…rated by the CMS (#59)

* FIX: Fixed issue where a crash could occur when an error page is generated by the CMS

* Added doc block

src/ErrorPageController.php

@@ -4,12 +4,24 @@
 use PageController;
 use SilverStripe\Control\HTTPRequest;
 use SilverStripe\Control\HTTPResponse;
+use SilverStripe\View\SSViewer;
 
 /**
  * Controller for ErrorPages.
  */
 class ErrorPageController extends PageController
 {
+    /**
+     * Explicitly set themes to the themes config value in case the theme was previously set to something else
+     * One example of this is when serving 404 error pages under the admin path e.g. admin/non-existent
+     * where LeftAndMain::init() will have previously set themes to the admin_themes config
+     */
+    protected function init()
+    {
+        SSViewer::set_themes(SSViewer::config()->themes);
+        parent::init();
+    }
+
     /**
      * Overload the provided {@link Controller::handleRequest()} to append the
      * correct status code post request since otherwise permission related error