[BUGFIX] Respect default values in TcaGroup

RelationHandler cannot handle vanilla uids, pass 0 instead to correctly parse defVals for MM-relations in TCA type=group

Resolves: #93289
Releases: master, 10.4, 9.5
Change-Id: I5258bbc5ef164fc9ed2d14ed1062b54e1f9eec92
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/67447


Tested-by: core-ci <typo3@b13.com>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Maik Schneider <schneider.maik@me.com>
Tested-by: Richard Haeser <richard@richardhaeser.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Maik Schneider <schneider.maik@me.com>
Reviewed-by: Richard Haeser <richard@richardhaeser.com>