Quick Settings: Fix flip-to-settings animation

Bug is reproduced as follows:

1. close the notification area while Quick Settings is showing
2. open the notification area, so that the notifications show
3. click the button on the top, to switch to quick settings.

Notice that only half of the animation is played. Having some
notifications shown helps visualizing it.

Change-Id: Iaabf16d7a17765dc7a12bcd5239d84fd6db96066