SystemUI: Don't try to update the navbar if it doesn't exist

Fix crashes on theme change on devices with buttons

Change-Id: I117c0ae605f7caca7e0f0425b80645a985644630
Correctly release lockscreen lock on tile destroy.

Change-Id: Idc5f9be9a42a800570bcf63118be293ed7760f5f
When DPM is updated while lock screen is inhibited, don't
unconditionally enable lock screen.

Change-Id: Iab2af06eb8e41fbcfc6adfbeb5b42a9bbf446fe9
Revert "Correctly release lockscreen lock on tile destroy."

This reverts commit 55e168ecfe67aaecbbe5fecf652268263f5ec532.