[BUGFIX] Avoid errors for creating new IRRE Elements on new parent records

This happens when the content element does not exist yet, which
is why this needs to be checked properly, otherwise the PHP strict
typing error will stop execution of the PHP script.

Resolves: #90801
Releases: master, 9.5
Change-Id: I94e5969a312ad876e9bd03b2c75b2de149ba3c61
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/63813


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Susanne Moog <look@susi.dev>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Susanne Moog <look@susi.dev>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>