[BUGFIX] Get folder’s identifier for exception message

The identifier of the folder object is now retrieved and used in the
exception message.

Resolves: #79194
Releases: master, 7.6
Change-Id: Iebea177434c6913bab705df119d750b497238252
Reviewed-on: https://review.typo3.org/51178


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Daniel Goerz <ervaude@gmail.com>
Tested-by: Daniel Goerz <ervaude@gmail.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>