[BUGFIX] Avoid undef array key in TcaRecordTitle

Resolves: #99582
Releases: main, 11.5
Change-Id: Ib7a0f546f025eed37bac6b494f29865494841787
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/77430


Reviewed-by: Nikita Hovratov <nikita.h@live.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Nikita Hovratov <nikita.h@live.de>
Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: core-ci <typo3@b13.com>

typo3/sysext/backend/Classes/Form/FormDataProvider/TcaRecordTitle.php

@@ -158,7 +158,7 @@ class TcaRecordTitle implements FormDataProviderInterface
             case 'inline':
                 $recordTitle = $this->getRecordTitleForInlineType(
                     $rawValue,
-                    $result['processedTca']['columns'][$fieldName]['children']
+                    $result['processedTca']['columns'][$fieldName]['children'] ?? []
                 );
                 break;
             case 'select':