[BUGFIX] Explicit cast to string for VersionState object

Some DB drivers are picky on their arguments not being
objects. Add an explicit cast to string for a VersionState
object just before it's fed to a query as argument.

Change-Id: I81c8f9dded7068ad7bf817e034aa67a29f28290c
Resolves: #81309
Releases: master, 8.7
Reviewed-on: https://review.typo3.org/52916


Reviewed-by: Claus Due <claus@phpmind.net>
Reviewed-by: Manuel Selbach <manuel_selbach@yahoo.de>
Tested-by: Manuel Selbach <manuel_selbach@yahoo.de>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>