[BUGFIX] CSS inline style for image border gets corrupted after saving

Resolves: #66844
Releases: master, 7.6, 6.2
Change-Id: I20fe7367433fe98a118890cc95306ee5e45504f4
Reviewed-on: https://review.typo3.org/48408


Tested-by: Marco Bresch <marco.bresch@starfinanz.de>
Reviewed-by: Marco Bresch <marco.bresch@starfinanz.de>
Reviewed-by: Jan Helke <typo3@helke.de>
Tested-by: Jan Helke <typo3@helke.de>