Adding users to Compare list does not work.

Change-Id: I079f0c8cf47213854c1ef358631b6a7c9ecc9260
Resolves: #41233
Releases: 6.0
Reviewed-on: http://review.typo3.org/15377
Reviewed-by: Mattias Nilsson
Reviewed-by: Helmut Hummel
Tested-by: Helmut Hummel
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters