fix warning: dereference of a null pointer

This fixes a warning: Access to field 'mPlaybackFormats' results
in a dereference of a null pointer (loaded from field 'mDeviceInfo')
[clang-analyzer-core.NullDereference]

Bug: None
Test: Static analyzer no longer complains, bullhead still boots with no
apparent issues.
Change-Id: I71ce486c667441d9b90ef63c2df8d23d70254639
1 file changed