[BUGFIX] Fix warning on array key "data"

Patch fixes warning on PHP 8.1 in MenuProcessor

Resolves: #98150
Releases: main, 11.5
Change-Id: I9cee1d6d0adcde22a74e040ac53657db3348c514
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/75475


Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>

typo3/sysext/frontend/Classes/DataProcessing/MenuProcessor.php

@@ -485,9 +485,9 @@ class MenuProcessor implements DataProcessorInterface
         }
         $request = $this->cObj->getRequest();
         $recordContentObjectRenderer = GeneralUtility::makeInstance(ContentObjectRenderer::class);
-        $recordContentObjectRenderer->start($page['data'], 'pages', $request);
-        $processedPage = $this->contentDataProcessor->process($recordContentObjectRenderer, $processorConfiguration, $page);
-        return $processedPage;
+        $recordContentObjectRenderer->start($page['data'] ?? [], 'pages', $request);
+
+        return $this->contentDataProcessor->process($recordContentObjectRenderer, $processorConfiguration, $page);
     }
 
     /**