~QApplication blocks with gdb if QQuickWidget isn't initialized completely

#include <QApplication>
#include <QQuickWidget>

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

  auto *w = new QQuickWidget();
  // w->engine(); // works fine if uncommented
  delete w;   // optional
  w = nullptr;// optional

  qWarning() << "Exit";
  return 0;
}