[BUGFIX] Avoid TypeError in extbase persistence

Properly check for the given value being an object before
passing it to corresponding method, which is type-hinted
since #100068.

Resolves: #100774
Related: #100068
Releases: main, 11.5
Change-Id: I704ef93ebbbfd1f161bf56dd7ef0058bd2b4875d
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/78918


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