Erro na class MainActivity

Bom dia,

Estou com um problema com minha class MainActivity, quando eu mando copilhar aparece uma mensagens de erro no console:

12-13 17:14:58.032 10363-10363/? E/AndroidRuntime: FATAL EXCEPTION: main
                                                   Process: com.example.guilherme.jumper, PID: 10363
                                                   java.lang.RuntimeException: Unable to resume activity {com.example.guilherme.jumper/com.example.guilherme.jumper.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.example.guilherme.jumper.engine.Game.inicia()' on a null object reference

                                                       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
                                                    Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.example.guilherme.jumper.engine.Game.inicia()' on a null object reference
                                                       at com.example.guilherme.jumper.MainActivity.onResume(MainActivity.java:28)

O erro esta falando que contrutor onResume este retornando null, aqui o meu codigo:

public class MainActivity extends AppCompatActivity {

    public Game game;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        FrameLayout container = findViewById(R.id.container);

        Game game = new Game(this);
        container.addView(game);
    }

    @Override
    protected void onResume() {
        super.onResume();
        this.game.inicia();
        new Thread(game).start();
    }

    @Override
    protected void onPause() {
        super.onPause();
        this.game.pausa();
    }
}

e também class Game:

public class Game extends SurfaceView implements Runnable {

    private boolean isRunning = true;
    private SurfaceHolder holder = getHolder();
    private passaro passaro_0;

    public Game(Context context) {
        super(context);

        inicializaElementos();
    }

    private void inicializaElementos() {
        passaro_0 = new passaro();
    }

    @Override
    public void run() {
        while(isRunning){  // desenho dos camponentes do jogo
            if (!holder.getSurface().isValid()) continue;
            Canvas canvas = holder.lockCanvas();

            passaro_0.desenhaNo(canvas);
            passaro_0.cai();

            holder.unlockCanvasAndPost(canvas);
        }
    }

    public void inicia() {
        isRunning = true;
    }

    public void pausa() {
        isRunning = false;
    }
}

Lembrando que eu estou utilizando android-studio3.0.1

Como eu posso resolver este erro?