[BUGFIX] Make sure correct data types are passed around in RefIndex

Releases: master, 8.7
Resolves: #81637
Change-Id: I8b5a1e701b91657efd341aae96a23f4c4d643b43
Reviewed-on: https://review.typo3.org/53293


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Johannes Fürnhammer <j.fuernhammer@siwa.at>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Jigal van Hemert <jigal.van.hemert@typo3.org>
Tested-by: Jigal van Hemert <jigal.van.hemert@typo3.org>