CefQuit crash at CefShutdown()

[abc100m]

app crash at CefShutdown() when quit

this issume can be fixed by :

change

MainWindow w;
w.show();
//a.setQuitOnLastWindowClosed(false);
result = a.exec();
-------------to------------------------------------
{
MainWindow w;
w.show();
//a.setQuitOnLastWindowClosed(false);
result = a.exec();
} // left w release first