Add null check to virtual device manager

Some tv targets are failing to boot after Ie10dbfe65bb3ab9d62ed5c7b5ed7095a51bccf24 with a null pointer on vdm. Adding null check.

Bug: 244116059
Bug: 244121297
Test: Forrest

Change-Id: Idb298213df6ddfda027fd51d0d532f0fcf47d32b
1 file changed