[BUGFIX] Cast tokenValue to string in ext:impexp

Cast 'tokenValue' to string as it can happen to be an integer.

Releases: master
Resolves: #95887
Change-Id: I2c053926a7ed24f6cc3634a8c139213de9b65f0f
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/72069


Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Oliver Bartsch <bo@cedev.de>