Merge "Add null check to work around async unregistration of receiver" into sc-dev

    private final BroadcastReceiver mBroadcastReceiver = new BroadcastReceiver() {

        @Override

        public void onReceive(Context context, Intent intent) {

            // TODO(193941146): Currently unregistering a receiver through BroadcastDispatcher is

            // async, but we've already cleared the fields. Just return early in this case.

            if (mNavigationBarView == null) {

                return;

            }

            String action = intent.getAction();

            if (Intent.ACTION_SCREEN_OFF.equals(action)

                    || Intent.ACTION_SCREEN_ON.equals(action)) {