fw: media: Handle NPE due to threading race

Change-Id: I6eab5bc3d687edfa6f0839e439b3314bed4fdcea
Temporarily hide lock screen unlock targets if opening a widget

If the user selects a widget to open, it's very unlikely that they would
want to use any of the slider shortcuts at that moment. Make it easier
to unlock the screen and open the desired widget by temporarily hiding
other targets.

Change-Id: I51d879cc77826e4f7235c5d35b6352e5e83bb7cf