[BUGFIX] utf8/multibyte character breaks menu filelist

Resolves: #51190
Releases: 6.2, 6.1
Change-Id: I105e23b12659495b4058edbc8091eee4374d58b9
Reviewed-on: https://review.typo3.org/23378
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters