Merge "Ignore null action in AppStateTrackerImpl." into main

    private final BroadcastReceiver mReceiver = new BroadcastReceiver() {

        @Override

        public void onReceive(Context context, Intent intent) {

            final String action = intent.getAction();

            if (action == null) {

                return;

            }

            final int userId = intent.getIntExtra(Intent.EXTRA_USER_HANDLE, -1);

            switch (intent.getAction()) {

            switch (action) {

                case Intent.ACTION_USER_REMOVED:

                    if (userId > 0) {

                        mHandler.doUserRemoved(userId);