[BUGFIX] Restore behavior of LocalDriver->isFolderEmpty()

With #92264 the behavior of the public function
LocalDriver->isFolderEmpty() has been changed for invalid
input. As this was an unintended change, the former behavior
is restored with this patch.

Resovles: #92498
Relates: #92264
Releases: master, 10.4
Change-Id: I4ab6d79b3ecacc575612391711ab039d62b64a90
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/66065


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>