[TASK] Address phpstan "Expression on left side of ??" errors

There are several PHPStan Baseline exceptions for misuse of
the ?? operator. Many of them are no longer necessary thanks
to either other code evolution or PHP evolution. This patch
cleans those up.

Resolves: #97456
Releases: main, 11.5
Change-Id: I47c23157398e80eb63e17455f820df3a6d756724
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/74619


Tested-by: core-ci <typo3@b13.com>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>