[BUGFIX] Add guard clause to prevent fataling on saving a CE

Resolves: #97270
Releases: main, 11.5
Change-Id: If1c899cdfd891cda5af5a502b40ab28c29830f58
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/74135


Tested-by: core-ci <typo3@b13.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>