Error with Class FireBase! (JAVA, ANDROID STUDIO)

Good Afternoon Friends !!

I downloaded a Source Code from a Taxi system, and I'm seeing some videos of the language in Java, but I'm encountering an error that I can not find, and when I give a biuld to generate a file in apk, it simply shows me 1 Error, with the Next Message!

(error: can not access zzbej class file for com.google.android.gms.internal.zzbej not found)

IntheErrorLogitpointstotheMyFirebaseMessagingService.javafilebutIcannotfindanerror,followtheCodebelow.

@OverridepublicvoidonMessageReceived(RemoteMessageremoteMessage){super.onMessageReceived(remoteMessage);sendNotification(remoteMessage.getData());}privatevoidsendNotification(Map<String,String>data){intnum=++NOTIFICATION_ID;Bundlemsg=newBundle();for(Stringkey:data.keySet()){Log.e(key,data.get(key));msg.putString(key,data.get(key));}Intentintent=newIntent(this,HomeActivity.class);if(msg.containsKey("action")) {
        intent.putExtra("action", msg.getString("action"));
    }
    intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
    PendingIntent pendingIntent = PendingIntent.getActivity(this, num /* Request code */, intent,
            PendingIntent.FLAG_ONE_SHOT);

    Uri defaultSoundUri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
    NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this)
            .setSmallIcon(R.drawable.icon)
            .setContentTitle(msg.getString("title"))
            .setContentText(msg.getString("msg"))
            .setAutoCancel(true)
            .setSound(defaultSoundUri)
            .setContentIntent(pendingIntent);

    NotificationManager notificationManager =
            (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);

    notificationManager.notify(num, notificationBuilder.build());
}

I hope you can help me, Vlw Galera.