Prevent NPE from onQueueChanged with a null queue

Bug: 78768610
Test: runtest bluetooth -c
com.android.bluetooth.avrcp.MediaPlayerWrapperTest
Change-Id: Ie8b8f96017bff20d54dbb06a620c235e8b8db1ae

(cherry picked from commit 6502f0f0e4cea84b2f470fffc10e84d344d9072d)
2 files changed