[BUGFIX] Prevent possible null pointer exception in data processors

The method `getContentObject()` might return null.
This is now properly handled in the MenuProcessor
and LanguageMenuProcessor.

Resolves: #99722
Releases: main, 11.5
Change-Id: Iebaa2324c59032bd10610c2a63156168777070db
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/77614


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