[BUGFIX] Restore compatibilty with TYPO3 9

Classes/Controller/ActionController.php

@@ -825,6 +825,7 @@ class ActionController extends BaseController
             );
         }
         $this->view->assignMultiple($result);
+        if (version_compare(TYPO3_branch, '10.0', '>=')) {
             return $this
                 ->responseFactory
                 ->createResponse()
@@ -833,4 +834,5 @@ class ActionController extends BaseController
                     (string)($html ?? $this->view->render()))
                 );
         }
+    }
 }

Configuration/TCA/Overrides/tt_content.php

@@ -1,5 +1,5 @@
 <?php
-defined('TYPO3') || die();
+defined('TYPO3_MODE') || die();
 
 \TYPO3\CMS\Extbase\Utility\ExtensionUtility::registerPlugin(
     'TemplatesAide',