Exception thrown at 0x5095FBC6 (sfml-system-d-2.dll)

#include "Game.h"
#include "SplashState.h"

namespace AFKGames {
  Game::Game(int width, int height, std::string title) {
    _data->window.create(sf::VideoMode(width, height), title, sf::Style::Default); // <----------------- error occurs
    _data->machine.AddState(StateRef(new SplashState(this->_data)));
    this->Run();
  }

  void Game::Run() {
    // MainLoop
  }
}

Run in Debug-Mode!!

Error Message: Exception thrown at 0x5095FBC6 (sfml-system-d-2.dll) in *.exe: 0xC0000005: Access Violation reading at Location 0xCCCCCCD8.

Any ideas?

Edit:

struct GameData {
    StateMachine machine;
    sf::RenderWindow window;
    AssetManager assets;
    InputManager input;
};

typedef std::shared_ptr<GameData> GameDataRef;

class Game {
public:
    Game(int width, int height, std::string title);

private:
    const float deltaTime = 1.0f / 60;
    sf::Clock _clock;

    GameDataRef _data = std::make_shared<GameData>(); //<-----------
    void Run();
};