[BUGFIX] Avoid undefined array key in UserInformationService

With empty permissions in a user to be compared, this
error does not appear anymore.

Resolves: #96793
Releases: main, 11.5
Change-Id: If6b632f67ce59e7cca0273b7672af87ed2ee257d
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/73361


Tested-by: core-ci <typo3@b13.com>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Oliver Hader <oliver.hader@typo3.org>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>