Fix handling of bad image previews.

When the image preview fails (eg for permissions or timeout) the entire
system area is removed. This prevents the user from using Nearby.

Instead, when the image preview fails, we should hide only the image
preview and leave the rest of the system area intact.

Bug: 168557188
Test: ChooserActivityTest; manual inspection
Change-Id: I49190c1fbc4e25b3d2e2802a90de355bff297f7e