Opening the preview of a single element from a workspace (meaning
click the eye icon in workspace module) opens the frontend preview,
where you can choose from visual changes and list view in the header.
Choosing the list view tab led to a file not found error due to double
typo3 in the iframe url.

Change-Id: Ie1ae3d5574359a471b844b9215449e02ef3a3f39
Resolves: #66281
Relates: #66052
Releases: master
Reviewed-on: http://review.typo3.org/38491


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Andreas Fernandez <andreas.fernandez@aspedia.de>
Tested-by: Andreas Fernandez <andreas.fernandez@aspedia.de>