[TYPO3-english] Typo 8.7.2 error saving content element forms

[Wim Spijker]

Wenn saving a content element with plugin Forms I get an error: In TYPO 8.7.1. there was no error, but on TYPO3 8.7.2:

Oops, an error occurred!
Argument 2 passed to TYPO3\CMS\Core\Database\ReferenceIndex::getRecordRawCached() must be of the type integer, null given, called in /home/wim/typo3_src-8.7.2/typo3/sysext/core/Classes/Database/ReferenceIndex.php on line 240