Add null check for vrManager

If VrManagerService is not started, vrManager will be null. Need
add check for it.

Test: system works fine whether device supports VR or not
Bug: 116427118
Change-Id: I924956234d9cd520e272a961b2939890164db1a5
Merged-In: I924956234d9cd520e272a961b2939890164db1a5
1 file changed