Quickfix of ButtonView Bug

The ButtonView of dynamically buttons like Redo, Undo and Delete altered if you touch the border of the Formula Editor Keyboard.

This Pullrequest fixes this issue.

Test (single UI): http://catrobatgw.ist.tugraz.at:8080/job/Catroid-single-UI-test/800/

![bugbuttonview_small](https://f.cloud.github.com/assets/1913681/586359/d5f85a38-c94b-11e2-933f-7ed2bde7a0d4.png)