[BUGFIX] Fix PHP 8 warning in ImageResourceContentObject

Added null coalescing operator in case $lastImgResourceInfo[3]
is not set.

Resolves: #99004
Releases: main, 11.5
Change-Id: Ieca6d193db884917785705b2468fcfe3ced623e2
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/77999


Tested-by: core-ci <typo3@b13.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Ralph Brugger <typo3bugs@public.linkpool.de>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Ralph Brugger <typo3bugs@public.linkpool.de>