Fix for bottom zero alert to play nice with TOC.

The bottom zero alert wan't fading out properly
when the Table of Contents was shown. Also was
causing issues with the bottom web view menu.
Rearranged the constraints so everything plays nice.

Change-Id: I6278bebc275e6ad943a4f9f269bba445d386a944
Merge "Fix for bottom zero alert to play nice with TOC."