The bug is still there. To reproduce:
- start kig
- klick on any construction tool in toolbar
- close window

Backtrace with today's master:

Application: Kig (kig), signal: Segmentation fault
[KCrash Handler]
#7  0xb60cdb00 in QScopedPointer<QObjectData, QScopedPointerDeleter<QObjectData> >::data (this=0x45454549) at ../../include/QtCore/../../../../git/Qt/frameworks/qt/src/corelib/tools/qscopedpointer.h:135
#8  0xb60cca43 in qGetPtrHelper<QScopedPointer<QObjectData> > (p=...) at ../../include/QtCore/../../../../git/Qt/frameworks/qt/src/corelib/global/qglobal.h:2434
#9  0xb60ccf1a in QAction::d_func (this=0x45454545) at /local/git/Qt/frameworks/qt/src/gui/kernel/qaction.h:67
#10 0xb60cb67b in QAction::setEnabled (this=0x45454545, b=false) at /local/git/Qt/frameworks/qt/src/gui/kernel/qaction.cpp:1113
#11 0xb21aefcd in KigMode::enableActions (this=0x8748608) at /local/git/KDE/edu/kig/modes/mode.cc:30
#12 0xb21b35f2 in NormalMode::enableActions (this=0x8748608) at /local/git/KDE/edu/kig/modes/normal.cc:48
#13 0xb220b539 in KigPart::setMode (this=0x87577a8, m=0x8748608) at /local/git/KDE/edu/kig/kig/kig_part.cpp:518
#14 0xb220c256 in KigPart::runMode (this=0x87577a8, m=0x87549c8) at /local/git/KDE/edu/kig/kig/kig_part.cpp:696
#15 0xb216af9c in ConstructibleAction::act (this=0x87bc6a0, d=...) at /local/git/KDE/edu/kig/misc/guiaction.cc:80
#16 0xb216b352 in KigGUIAction::slotActivated (this=0x87f4c88) at /local/git/KDE/edu/kig/misc/guiaction.cc:106
#17 0xb216ac44 in KigGUIAction::qt_static_metacall (_o=0x87f4c88, _c=QMetaObject::InvokeMetaMethod, _id=0, _a=0xbffcca88) at /local/build/KDE/edu/kig/guiaction.moc:49
#18 0xb5a38e0e in QMetaObject::activate (sender=0x87f4c88, m=0xb6bf37a8, local_signal_index=1, argv=0xbffcca88) at /local/git/Qt/frameworks/qt/src/corelib/kernel/qobject.cpp:3547
#19 0xb60cc92a in QAction::triggered (this=0x87f4c88, _t1=false) at .moc/debug-shared/moc_qaction.cpp:277
#20 0xb60cbd69 in QAction::activate (this=0x87f4c88, event=QAction::Trigger) at /local/git/Qt/frameworks/qt/src/gui/kernel/qaction.cpp:1257
#21 0xb60ccf89 in QAction::trigger (this=0x87f4c88) at /local/git/Qt/frameworks/qt/src/gui/kernel/qaction.h:218
#22 0xb6641887 in QToolButton::nextCheckState (this=0x8841798) at /local/git/Qt/frameworks/qt/src/gui/widgets/qtoolbutton.cpp:1144
#23 0xb6548c26 in QAbstractButtonPrivate::click (this=0x8841a78) at /local/git/Qt/frameworks/qt/src/gui/widgets/qabstractbutton.cpp:530
#24 0xb654a0a7 in QAbstractButton::mouseReleaseEvent (this=0x8841798, e=0xbffcd324) at /local/git/Qt/frameworks/qt/src/gui/widgets/qabstractbutton.cpp:1123
#25 0xb66401c6 in QToolButton::mouseReleaseEvent (this=0x8841798, e=0xbffcd324) at /local/git/Qt/frameworks/qt/src/gui/widgets/qtoolbutton.cpp:718
#26 0xb613b01d in QWidget::event (this=0x8841798, event=0xbffcd324) at /local/git/Qt/frameworks/qt/src/gui/kernel/qwidget.cpp:8371
#27 0xb6549f18 in QAbstractButton::event (this=0x8841798, e=0xbffcd324) at /local/git/Qt/frameworks/qt/src/gui/widgets/qabstractbutton.cpp:1082
#28 0xb66418fc in QToolButton::event (this=0x8841798, event=0xbffcd324) at /local/git/Qt/frameworks/qt/src/gui/widgets/qtoolbutton.cpp:1160
#29 0xb60db280 in QApplicationPrivate::notify_helper (this=0x861b2a8, receiver=0x8841798, e=0xbffcd324) at /local/git/Qt/frameworks/qt/src/gui/kernel/qapplication.cpp:4551
#30 0xb60d93b1 in QApplication::notify (this=0xbffcdac4, receiver=0x8841798, e=0xbffcd324) at /local/git/Qt/frameworks/qt/src/gui/kernel/qapplication.cpp:4094
#31 0xb6e21a3a in KApplication::notify (this=0xbffcdac4, receiver=0x8841798, event=0xbffcd324) at /local/git/KDE/libs/kdelibs/kdeui/kernel/kapplication.cpp:311
#32 0xb5a1d0a6 in QCoreApplication::notifyInternal (this=0xbffcdac4, receiver=0x8841798, event=0xbffcd324) at /local/git/Qt/frameworks/qt/src/corelib/kernel/qcoreapplication.cpp:915
#33 0xb60ddc63 in QCoreApplication::sendSpontaneousEvent (receiver=0x8841798, event=0xbffcd324) at ../../include/QtCore/../../../../git/Qt/frameworks/qt/src/corelib/kernel/qcoreapplication.h:234
#34 0xb60d7b35 in QApplicationPrivate::sendMouseEvent (receiver=0x8841798, event=0xbffcd324, alienWidget=0x8841798, nativeWidget=0x88405f8, buttonDown=0xb6c124e0, lastMouseReceiver=..., spontaneous=true) at /local/git/Qt/frameworks/qt/src/gui/kernel/qapplication.cpp:3160
#35 0xb6172ced in QETWidget::translateMouseEvent (this=0x88405f8, event=0xbffcd7f0) at /local/git/Qt/frameworks/qt/src/gui/kernel/qapplication_x11.cpp:4502
#36 0xb616f886 in QApplication::x11ProcessEvent (this=0xbffcdac4, event=0xbffcd7f0) at /local/git/Qt/frameworks/qt/src/gui/kernel/qapplication_x11.cpp:3503
#37 0xb61a6461 in x11EventSourceDispatch (s=0x861ae28, callback=0, user_data=0x0) at /local/git/Qt/frameworks/qt/src/gui/kernel/qguieventdispatcher_glib.cpp:146
#38 0xb4c0a863 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#39 0xb4c0ac00 in ?? () from /usr/lib/libglib-2.0.so.0
#40 0xb4c0ace1 in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#41 0xb5a54cfe in QEventDispatcherGlib::processEvents (this=0x860ed10, flags=...) at /local/git/Qt/frameworks/qt/src/corelib/kernel/qeventdispatcher_glib.cpp:424
#42 0xb61a67b6 in QGuiEventDispatcherGlib::processEvents (this=0x860ed10, flags=...) at /local/git/Qt/frameworks/qt/src/gui/kernel/qguieventdispatcher_glib.cpp:204
#43 0xb5a1a755 in QEventLoop::processEvents (this=0xbffcda6c, flags=...) at /local/git/Qt/frameworks/qt/src/corelib/kernel/qeventloop.cpp:149
#44 0xb5a1a8cd in QEventLoop::exec (this=0xbffcda6c, flags=...) at /local/git/Qt/frameworks/qt/src/corelib/kernel/qeventloop.cpp:204
#45 0xb5a1d73c in QCoreApplication::exec () at /local/git/Qt/frameworks/qt/src/corelib/kernel/qcoreapplication.cpp:1187
#46 0xb60d8796 in QApplication::exec () at /local/git/Qt/frameworks/qt/src/gui/kernel/qapplication.cpp:3812
#47 0x0804ecca in main (argc=1, argv=0xbffcdc14) at /local/git/KDE/edu/kig/kig/main.cpp:141