[BUGFIX] Fix rendering SVG icons in FormEngine

Resolves: #68452
Releases: master
Change-Id: I7a6b908ff650ad39f09e6610c405b5a520696a62
Reviewed-on: http://review.typo3.org/41797


Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Reviewed-by: Susanne Moog <typo3@susannemoog.de>
Tested-by: Susanne Moog <typo3@susannemoog.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>