Why does my qt program break in the click function?

Question

Qt

In my game, the first mouse click is the choice of checkers, the second where the move will be made. But the first time I click, the program breaks. How to fix it? Please help, please
Link to the project - dropmefiles.com/SMUYd

Answer 1

mainwindow.cpp, lines 317-320:

while (isAvaliable(x, y) != true) {
    x = se->scenePos().x()/50;
    y = se->scenePos().y()/50;
}

Loop - infinite, isAvaliable never returns true