[TASK] Protect methods in ElementBrowserController

Resolves: #86192
Releases: master
Change-Id: Id7076427c911af750748e47902e87c1c48b2d2d7
Reviewed-on: https://review.typo3.org/58222


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Frans Saris <franssaris@gmail.com>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>