Fix possible NPE + and missing expandable panel

Steps to reproduce for NPE:
- go into volume style settings
- switch to disabled
- switch to expanded
- NPE and hotreboot

Fix:
Check if mStreamControls is initialized and if not lock it and do it.

Steps for expandable error:
- go into volume style settings
- switch to disable
- press one time the volume button
- change to expandable
- change the volume and press the expanded icon
- result is it does not expand and is empty due of the missing volume panels.

Fix:
- if it was changed from disabled to expanded be sure that the additional volume panels
are recreated.

PS:
- fix another exception

Change-Id: I58d63d34f831b6a6f60f6eddb3a07fc916d464f3
Fix another possible NPE + and missing expandable panel correction

Thanks Jorge for pointing it out. This version is way nicer.

Change-Id: I7a65a05ef533c90cbfc68d4de996eae7a0ff66b7
Fix Volume panel background [Dark UI]

Volume panel is a bit out of the box compared to the normal theming.
Reapply the background via java code on theme change.

Change-Id: I0df41a95487f7c23d5fda5c2ec7df763c8e2f466

Conflicts:
	core/java/android/view/VolumePanel.java
	core/res/res/values/slim_symbols.xml