[BUGFIX] Fix various undefined array key errors in PHP8

Resolves: #95925
Releases: master
Change-Id: I125fcb5e60561646ee8398b0536106a2d5c828ed
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/72103


Tested-by: core-ci <typo3@b13.com>
Tested-by: Nikita Hovratov <nikita.h@live.de>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Nikita Hovratov <nikita.h@live.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>