[BUGFIX] Ensure Frontend Group identifiers are not empty in SQL clause

Change-Id: I18f1a0d0c28f66851f50a7106e681d96e64f1a2d
Releases: 3.0.0
Resolves: #59403
Reviewed-on: https://review.typo3.org/30622
Reviewed-by: Fabien Udriot
Tested-by: Fabien Udriot