Ninja bottom bar

[GalaxyNexus, 4.2.1, MasterHEAD: 6c9b86be27ff...]

Bug: Type in a wrong formula in the Formula Editor f.e. "1 +" and then press 'BACK'.
Suddenly the bottom bar with 'PLAY'- and 'ADD'-button appears!
Moreover if you use this bottom bar the app does some fancy stuff and crashes.

This pullrequest fixes this issue.

Test(s): 
http://catrobatgw.ist.tugraz.at:8080/job/Catroid-custom-branch-test/1160/
http://catrobatgw.ist.tugraz.at:8080/job/Catroid-custom-branch-test/1163/
http://catrobatgw.ist.tugraz.at:8080/job/Catroid-custom-branch-test/1170/

![ninjabottombar_small](https://f.cloud.github.com/assets/1913681/590044/0847ac12-c9d5-11e2-8472-cb0e2c95f447.png)