[BUGFIX] PHP7.2: Check value for NULL before count

Resolves: #82322
Releases: master, 8.7, 7.6
Change-Id: I31f7bc2db61337e10be7ffd44ac294b77c44d07b
Reviewed-on: https://review.typo3.org/53939


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>