RMB over QGraphicsTextItem causes a crash

#0  0x00007ffff7859e53 in QFlags<Qt::WindowType>::operator& (this=0x18d, other=Qt::WindowType_Mask)
    at ../../include/QtCore/../../../../qt-515/qtbase/src/corelib/global/qflags.h:146
#1  0x00007ffff785914b in QWidget::windowType (this=0x6d6d30)
    at ../../include/QtWidgets/../../../../qt-515/qtbase/src/widgets/kernel/qwidget.h:769
#2  0x00007ffff7859174 in QWidget::isWindow (this=0x6d6d30)
    at ../../include/QtWidgets/../../../../qt-515/qtbase/src/widgets/kernel/qwidget.h:777
#3  0x00007ffff78916a2 in QWidget::window (this=0x6d6d30)
    at /home/jarek/dev/qt-515/qtbase/src/widgets/kernel/qwidget.cpp:4139
#4  0x00007ffff7ad6c29 in QWidgetTextControlPrivate::contextMenuEvent (this=0x7fffe0007b70, screenPos=..., 
    docPos=..., contextWidget=0x0) at /home/jarek/dev/qt-515/qtbase/src/widgets/widgets/qwidgettextcontrol.cpp:1945
#5  0x00007ffff7ad33e5 in QWidgetTextControl::processEvent (this=0x6e27e0, e=0x7fffffffb8e0, transform=..., 
    contextWidget=0x0) at /home/jarek/dev/qt-515/qtbase/src/widgets/widgets/qwidgettextcontrol.cpp:1133
#6  0x00007ffff7ad2821 in QWidgetTextControl::processEvent (this=0x6e27e0, e=0x7fffffffb8e0, coordinateOffset=..., 
    contextWidget=0x0) at /home/jarek/dev/qt-515/qtbase/src/widgets/widgets/qwidgettextcontrol.cpp:998
#7  0x00007ffff7c425a2 in QGraphicsTextItemPrivate::sendControlEvent (this=0x6e3ab0, e=0x7fffffffb8e0)
    at /home/jarek/dev/qt-515/qtbase/src/widgets/graphicsview/qgraphicsitem.cpp:9966
#8  0x00007ffff7c39b29 in QGraphicsTextItem::contextMenuEvent (this=0x6d6d30, event=0x7fffffffb8e0)
    at /home/jarek/dev/qt-515/qtbase/src/widgets/graphicsview/qgraphicsitem.cpp:10405
#9  0x00007ffff7c32934 in QGraphicsItem::sceneEvent (this=0x6d6d40, event=0x7fffffffb8e0)
    at /home/jarek/dev/qt-515/qtbase/src/widgets/graphicsview/qgraphicsitem.cpp:6898
#10 0x00007ffff7c39550 in QGraphicsTextItem::sceneEvent (this=0x6d6d30, event=0x7fffffffb8e0)
    at /home/jarek/dev/qt-515/qtbase/src/widgets/graphicsview/qgraphicsitem.cpp:10280
#11 0x00007ffff7c5bacc in QGraphicsScenePrivate::sendEvent (this=0x5ecd40, item=0x6d6d40, event=0x7fffffffb8e0)
    at /home/jarek/dev/qt-515/qtbase/src/widgets/graphicsview/qgraphicsscene.cpp:1258
#12 0x00007ffff7c62330 in QGraphicsScene::contextMenuEvent (this=0x654500, contextMenuEvent=0x7fffffffb8e0)
    at /home/jarek/dev/qt-515/qtbase/src/widgets/graphicsview/qgraphicsscene.cpp:3603
#13 0x00007ffff7c6174b in QGraphicsScene::event (this=0x654500, event=0x7fffffffb8e0)
    at /home/jarek/dev/qt-515/qtbase/src/widgets/graphicsview/qgraphicsscene.cpp:3390
#14 0x00007ffff7855859 in QApplicationPrivate::notify_helper (this=0x4491e0, receiver=0x654500, e=0x7fffffffb8e0)
    at /home/jarek/dev/qt-515/qtbase/src/widgets/kernel/qapplication.cpp:3632
#15 0x00007ffff7852d0f in QApplication::notify (this=0x7fffffffd690, receiver=0x654500, e=0x7fffffffb8e0)
    at /home/jarek/dev/qt-515/qtbase/src/widgets/kernel/qapplication.cpp:2972
#16 0x00007ffff69b8378 in QCoreApplication::notifyInternal2 (receiver=0x654500, event=0x7fffffffb8e0)
    at /home/jarek/dev/qt-515/qtbase/src/corelib/kernel/qcoreapplication.cpp:1064
#17 0x00007ffff69b8d10 in QCoreApplication::sendEvent (receiver=0x654500, event=0x7fffffffb8e0)
    at /home/jarek/dev/qt-515/qtbase/src/corelib/kernel/qcoreapplication.cpp:1459
#18 0x00007ffff7c9bc92 in QGraphicsView::contextMenuEvent (this=0x633460, event=0x7fffffffc4a0)
    at /home/jarek/dev/qt-515/qtbase/src/widgets/graphicsview/qgraphicsview.cpp:3040
#19 0x00007ffff789f68b in QWidget::event (this=0x633460, event=0x7fffffffc4a0)
    at /home/jarek/dev/qt-515/qtbase/src/widgets/kernel/qwidget.cpp:8823
#20 0x00007ffff798eae3 in QFrame::event (this=0x633460, e=0x7fffffffc4a0)
    at /home/jarek/dev/qt-515/qtbase/src/widgets/widgets/qframe.cpp:550
#21 0x00007ffff7992694 in QAbstractScrollArea::viewportEvent (this=0x633460, e=0x7fffffffc4a0)
    at /home/jarek/dev/qt-515/qtbase/src/widgets/widgets/qabstractscrollarea.cpp:1095
#22 0x00007ffff7c9baa0 in QGraphicsView::viewportEvent (this=0x633460, event=0x7fffffffc4a0)
    at /home/jarek/dev/qt-515/qtbase/src/widgets/graphicsview/qgraphicsview.cpp:3014
#23 0x00007ffff7993a6b in QAbstractScrollAreaPrivate::viewportEvent (this=0x632bb0, event=0x7fffffffc4a0)
    at /home/jarek/dev/qt-515/qtbase/src/widgets/widgets/qabstractscrollarea_p.h:111
#24 0x00007ffff7993b38 in QAbstractScrollAreaFilter::eventFilter (this=0x607850, o=0x631a20, e=0x7fffffffc4a0)
    at /home/jarek/dev/qt-515/qtbase/src/widgets/widgets/qabstractscrollarea_p.h:122
#25 0x00007ffff69b879d in QCoreApplicationPrivate::sendThroughObjectEventFilters (receiver=0x631a20, 
    event=0x7fffffffc4a0) at /home/jarek/dev/qt-515/qtbase/src/corelib/kernel/qcoreapplication.cpp:1190
#26 0x00007ffff785582d in QApplicationPrivate::notify_helper (this=0x4491e0, receiver=0x631a20, e=0x7fffffffc4a0)
    at /home/jarek/dev/qt-515/qtbase/src/widgets/kernel/qapplication.cpp:3626
#27 0x00007ffff7853f07 in QApplication::notify (this=0x7fffffffd690, receiver=0x631a20, e=0x7fffffffc4a0)
    at /home/jarek/dev/qt-515/qtbase/src/widgets/kernel/qapplication.cpp:3238
#28 0x00007ffff69b8378 in QCoreApplication::notifyInternal2 (receiver=0x631a20, event=0x7fffffffc4a0)
    at /home/jarek/dev/qt-515/qtbase/src/corelib/kernel/qcoreapplication.cpp:1064
#29 0x00007ffff69b8404 in QCoreApplication::forwardEvent (receiver=0x631a20, event=0x7fffffffc4a0, 
    originatingEvent=0x7fffffffcfd0) at /home/jarek/dev/qt-515/qtbase/src/corelib/kernel/qcoreapplication.cpp:1079
#30 0x00007ffff78cdf7e in QWidgetWindow::handleMouseEvent (this=0x632170, event=0x7fffffffcfd0)
    at /home/jarek/dev/qt-515/qtbase/src/widgets/kernel/qwidgetwindow.cpp:691
#31 0x00007ffff78cc6ea in QWidgetWindow::event (this=0x632170, event=0x7fffffffcfd0)
    at /home/jarek/dev/qt-515/qtbase/src/widgets/kernel/qwidgetwindow.cpp:300
#32 0x00007ffff7855859 in QApplicationPrivate::notify_helper (this=0x4491e0, receiver=0x632170, e=0x7fffffffcfd0)
    at /home/jarek/dev/qt-515/qtbase/src/widgets/kernel/qapplication.cpp:3632
#33 0x00007ffff7852d0f in QApplication::notify (this=0x7fffffffd690, receiver=0x632170, e=0x7fffffffcfd0)
    at /home/jarek/dev/qt-515/qtbase/src/widgets/kernel/qapplication.cpp:2972
#34 0x00007ffff69b8378 in QCoreApplication::notifyInternal2 (receiver=0x632170, event=0x7fffffffcfd0)
    at /home/jarek/dev/qt-515/qtbase/src/corelib/kernel/qcoreapplication.cpp:1064
#35 0x00007ffff69b8d4a in QCoreApplication::sendSpontaneousEvent (receiver=0x632170, event=0x7fffffffcfd0)
    at /home/jarek/dev/qt-515/qtbase/src/corelib/kernel/qcoreapplication.cpp:1471
#36 0x00007ffff6eebdcb in QGuiApplicationPrivate::processMouseEvent (e=0x6e1970)
    at /home/jarek/dev/qt-515/qtbase/src/gui/kernel/qguiapplication.cpp:2282
#37 0x00007ffff6eeb019 in QGuiApplicationPrivate::processWindowSystemEvent (e=0x6e1970)
    at /home/jarek/dev/qt-515/qtbase/src/gui/kernel/qguiapplication.cpp:2002
#38 0x00007ffff6ecb6a2 in QWindowSystemInterface::sendWindowSystemEvents (flags=...)
    at /home/jarek/dev/qt-515/qtbase/src/gui/kernel/qwindowsysteminterface.cpp:1169
#39 0x00007fffe6421167 in xcbSourceDispatch (source=0x5169f0)
    at /home/jarek/dev/qt-515/qtbase/src/plugins/platforms/xcb/qxcbeventdispatcher.cpp:105
#40 0x00007ffff3dfc96f in g_main_context_dispatch () from /lib64/libglib-2.0.so.0
#41 0x00007ffff3e4e758 in g_main_context_iterate.constprop () from /lib64/libglib-2.0.so.0
#42 0x00007ffff3df9d43 in g_main_context_iteration () from /lib64/libglib-2.0.so.0
#43 0x00007ffff6a472c6 in QEventDispatcherGlib::processEvents (this=0x5100d0, flags=...)
    at /home/jarek/dev/qt-515/qtbase/src/corelib/kernel/qeventdispatcher_glib.cpp:423
#44 0x00007fffe6421384 in QXcbGlibEventDispatcher::processEvents (this=0x5100d0, flags=...)
    at /home/jarek/dev/qt-515/qtbase/src/plugins/platforms/xcb/qxcbeventdispatcher.cpp:143
#45 0x00007ffff69b4e5f in QEventLoop::processEvents (this=0x7fffffffd4a0, flags=...)
    at /home/jarek/dev/qt-515/qtbase/src/corelib/kernel/qeventloop.cpp:139
#46 0x00007ffff69b516c in QEventLoop::exec (this=0x7fffffffd4a0, flags=...)
    at /home/jarek/dev/qt-515/qtbase/src/corelib/kernel/qeventloop.cpp:232
#47 0x00007ffff69b8b67 in QCoreApplication::exec ()
    at /home/jarek/dev/qt-515/qtbase/src/corelib/kernel/qcoreapplication.cpp:1372
#48 0x00007ffff6eeaa7c in QGuiApplication::exec ()
    at /home/jarek/dev/qt-515/qtbase/src/gui/kernel/qguiapplication.cpp:1867
#49 0x00007ffff785270f in QApplication::exec ()
    at /home/jarek/dev/qt-515/qtbase/src/widgets/kernel/qapplication.cpp:2824
#50 0x0000000000416df0 in main (argv=1, args=0x7fffffffd7a8)
    at ../../dev/qt-dev/qtbase/examples/widgets/graphicsview/diagramscene/main.cpp:64