C++ SFML 0xCCCCCCCC acess violation error

Question

I'm trying to learn C++. I'm trying to get into GUI-programming with the frame work SFML (based on OpenGL) and TGUI. When I run my basic program (just window initialisation and creating a button) in Visual Studio (debug mode), it throws the exception: Access violation reading location 0xCCCCCCCC. I found out, that 0xCCCCCCCC is a specific memory pattern and means I am doing stuff with uninitialised memory on the stack. But where am I doing this in my program? My Code:

#include <TGUI/Gui.hpp>
#include <TGUI\TGUI.hpp>
#include <TGUI\Widgets\Button.hpp>

using namespace std;

int main() {
    tgui::Button::Ptr button = tgui::Button::create("Test");   //HERE THE EXCEPTION IS THROWN
    sf::RenderWindow window(sf::VideoMode(800, 600), "Fenster");
    tgui::Gui gui(window);
    gui.add(button, "Hallo");

    while (window.isOpen())
    {
        sf::Event event;
        while (window.pollEvent(event))
        {
            // When the window is closed, the application ends
            if (event.type == sf::Event::Closed)
            {
                window.close();
            } else if (event.type == sf::Event::Resized){
                window.setView(sf::View(sf::FloatRect(0, 0, event.size.width, event.size.height)));
                gui.setView(window.getView());
            }

            // Pass the event to all the widgets
            gui.handleEvent(event);
        }

        window.clear();

        // Draw all created widgets
        gui.draw();

        window.display();
    }

delete button;
button = NULL; 
return EXIT_SUCCESS;
}

Any help would be nice. Thanks!