Popups get enter event on mouse release if mouse button was down when popup opened.

Popups get enter event on mouse release if mouse button was down when popup opened. This results in QWidget::underMouse() for popup reporting true incorrectly until mouse actually enters and leaves the popup. Incorrect undermouse state blocks QCompleter from closing its popup.

This seems to be caused by the fact that QWidgetWindow::handleMouseEvent() always gives m_widget for QApplicationPrivate::sendMouseEvent() as native widget, even if mouse event happens outside m_widget.