[BUGFIX] Filebrowser: Plus-Sign disappear for not-selectable items now

Resolves: #76408
Releases: master, 7.6
Change-Id: I20cfc02b588776f4e76980aa68dfe5c032103563
Reviewed-on: https://review.typo3.org/50786


Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Kevin Ditscheid <kevinditscheid@gmail.com>
Reviewed-by: Joerg Boesche <typo3@joergboesche.de>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Gleb Levitin <gleb.levitin@dkd.de>
Tested-by: Gleb Levitin <gleb.levitin@dkd.de>
Reviewed-by: Jan Helke <typo3@helke.de>
Tested-by: Jan Helke <typo3@helke.de>