[BUGFIX] Fix PHP 8 notices in workspaces preview

Resolves: #96430
Releases: main, 11.5
Change-Id: I8569537d90ee5dc74157db4f3e583366b82a2e27
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/72800


Reviewed-by: Simon Gilli <typo3@gilbertsoft.org>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Simon Gilli <typo3@gilbertsoft.org>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Benni Mack <benni@typo3.org>