[BUGFIX] Add fallback values for frontend

For PHP8 in the frontend there are still
undefined key warnings.

This is fixed by adding fallbacks.

Resolves: #95082
Releases: master
Change-Id: I4ef512366aeb3b53adba4e96b07869657415b55d
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/70867


Tested-by: core-ci <typo3@b13.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Oliver Bartsch <bo@cedev.de>