UserVariable Bricks Spinner Update Fix

Fixes #454

Test (custom-branch-no-emma): http://catrobatgw.ist.tugraz.at:8080/job/Catroid-custom-branch-no-emma-test/63/
http://catrobatgw.ist.tugraz.at:8080/job/Catroid-custom-branch-no-emma-test/64/
http://catrobatgw.ist.tugraz.at:8080/job/Catroid-custom-branch-no-emma-test/66/
http://catrobatgw.ist.tugraz.at:8080/job/Catroid-custom-branch-no-emma-test/67/