Add null check for vrManager

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

Test: system does not break if VrManagerService is not started
Bug: 116427118
Change-Id: I05ec75c73d11365e0b7bbaa603d0e96309d6fd1d
Merged-In: I05ec75c73d11365e0b7bbaa603d0e96309d6fd1d
1 file changed