[BUGFIX] Add fallback for undefined array key - versionNumberInFilename

[BE]versionNumberInFilename set to "true" triggers a
undefined key warning in PHP8.

This has been fixed by testing for a empty value
in the array key.

Resolves: #95223
Releases: master
Change-Id: I3b88010d73e6e459819bbbfbe6751a4b2fb7f8f0
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/71090


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