If you trigger mouse binding for Window Scale when already scaled, it will crash

[Marco Bettiolo]

I am using Ubuntu 14.04 LTS with the Unity UI.

I have bound the Compiz Scale plugin to the TopLeft corner, to Super+W and to the mouse10 mouse button.

Reproduction:
- Initiate the scale with the TopLeft corner or with Super+W
- While in the scaled view, trigger the mouse10 mouse button

BUG: As a result, the scale view will never go back to the normal view. It is now stuck to the scale view. Clicking on a window or on an empty space does not return the UI to the normal state.

You need to reset the UI with "unity --replace" to be able to use the system.

Thanks
Marco Bettiolo