[BUGFIX] Add guard clause to prevent Link Browser from fataling

Resolves: #97269
Releases: main, 11.5
Change-Id: Iec86d579af4fa8774f7ba6bd4d6b137ccefe3dd5
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/74125


Tested-by: core-ci <typo3@b13.com>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Oliver Bartsch <bo@cedev.de>