[BUGFIX] RTE: Quick Tag plugin may raise JS exception in Google Chrome

A JavaScript exception may be raised in Google Chrome on attempt to
access a style sheet on a different domain.

Releases: master
Resolves: #63716
Change-Id: I16b5eb5630e0d4855023bb3ec7e5344574460cad
Reviewed-on: http://review.typo3.org/35204
Reviewed-by: Stanislas Rolland <typo3@sjbr.ca>
Tested-by: Stanislas Rolland <typo3@sjbr.ca>