[BUGFIX] RTE-Icon not working

Change-Id: Ifa549795b9040074272605dcec3261d0a4b441e4
Releases: 3.0.0
Resolves: #60518
Reviewed-on: http://review.typo3.org/31775
Reviewed-by: Fabien Udriot <fabien.udriot@ecodev.ch>
Tested-by: Fabien Udriot <fabien.udriot@ecodev.ch>