Crash in qt_try_modal ( top is NULL )

I've found a bug in qtbase\src\widgets\kernel\qapplication_qpa.cpp in function:
bool qt_try_modal(QWidget *widget, QEvent::Type type)

There is NULL in variable "top" so instruction
if ((block_event || paint_event) && top->parentWidget() == 0)
top->raise();
makes a crash.

This crash is connected to modality.

There is minimal example of qml :

import QtQuick 2.1
import QtQuick.Controls 1.0
import QtQuick.Window 2.0

Window {
width: 640
height: 480
modality: Qt.ApplicationModal

Button

{ text: qsTr("Move mouse cursor on me") anchors.horizontalCenter: parent.horizontalCenter anchors.verticalCenter: parent.verticalCenter tooltip: "Move mouse cursor on me and hold till crash" }

}

Regards,
Alex