[TASK] Fix PHP 8 compatibility issues part 3/x

PHP 8 throws warning level errors instead of
notice level errors when an not existing array
key is accessed.
The patch fixes another batch of this kind of
issues found by functional tests.

Resolves: #93675
Releases: master
Change-Id: I88e2a0a28af21a95b9ec3e74c7449d9cdc7a23bc
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/68234


Tested-by: Jochen <rothjochen@gmail.com>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Richard Haeser <richard@richardhaeser.com>
Reviewed-by: Jochen <rothjochen@gmail.com>
Reviewed-by: Richard Haeser <richard@richardhaeser.com>