Support set active device to null.

Since some process will call removeActiveDevice for setting device to
null. But below current logic, if the device is null will skip the
action. The patch is that add check if the deivce is null, will directly
set the active to null.

Bug: 152581026
Test: Manual
Change-Id: Ib4c00d75e0de0581abf993469a029e02d36d608e
Merged-In: Ib4c00d75e0de0581abf993469a029e02d36d608e
1 file changed