On PHP 8.0, renaming a folder in the backend might fail
with a "PHP Warning: Uninitialized string offset 0". This
is fixed by utilizing the substr() function instead.

Resolves: #95273
Releases: master
Change-Id: Ib642a25492c933b6fae857206c4535b7a861cc3c
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/71123


Tested-by: core-ci <typo3@b13.com>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>