Game crashes and music won't stop playing.

This is an issue we've had occasionally with different games we're developing. All made with UE4. The game crashes but the music keeps playing. Even in the menu, when the headset is in standby mode and when you launch another game. Logcat is spammed with : 

09-02 16:35:26.536 29785 29823 W System.err: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.graphics.Bitmap.getWidth()' on a null object reference
09-02 16:35:26.536 29785 29823 W System.err:    at com.unity3d.player.FrameAnimation.b(Unknown Source)
09-02 16:35:26.536 29785 29823 W System.err:    at com.unity3d.player.FrameAnimation.run(Unknown Source)

Can't find anything else related to this in the logs. Can post an adb bugreport if it helps.