Fix IllegalStateException in MyProjectsActivityTest

Should fix the IllegalStateException in the MyProjectsActivityTest, which occurs very often on the master branch.

I don't know exactly why the ListView is not updated when a Sprite is added, but this quick fix with a solo.sleep before adding the Sprite should solve the problem.

MyProjectsActivityTest (run 3 times):
http://catrobatgw.ist.tugraz.at:8080/job/Catroid-single-UI-test/656/