A QComboBox with a popup will crash when the popup is dismissed with the mouse (clicking on arrow). This happens because it believes there is a close button there as if there were a (hidden) system menu. The situation is reproduced if QWasmWindow::injectMouseReleased calls window()->close() when the popup window of a QComboBox is dismissed.

#include <QApplication>
#include <QComboBox>

int
main(int argc,char *argv[])
{
        QApplication a( argc, argv );

        QComboBox w;
        w.addItem("1");
        w.addItem("2");
        w.addItem("3");
        w.addItem("4");
        w.setEditable(true);
        w.show();

        return a.exec();
}