[BUGFIX] Prevent PHP 8 warnings during content rendering

Prevent access to undefined array keys in content renderer
and menu objects.

Resolves: #95489
Releases: master
Change-Id: I1ec4b046478e7e83176e1178153d57a2890b269e
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/71454


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