Themes: uninstallThemeForAllApps shouldn't check if map is empty if it's null

Potential NPE introduced in ec2200878706735cdd2caf4d934d988296998e85

Change-Id: I6d1ec165957c2be63086a18af2236e46978e9c8a
UsbDebuggingManager : Handle race condition when toggling rapidly

When toggling adb enable/disable rapidly, you can have the situation where the thread's
run() gets invoked but mAdbEnabled is already set to false, hence listenToSocket() never even
gets invoked in which case mOutputStream/mSocket are both null. This patchset adds checks
around that.

Change-Id: Iba56e7409435e22d690432fa663bc0a04a1a447d