Sometimes for unknown reason and after some hours of using the desktop, while I right click on the title of a window and select Activities kwin crashes and restarts and my windows activities are reset.

Reproducible: Sometimes

Steps to Reproduce:
1. Use activities and put some windows on different ones
2. after some time (usually hours) right click on the title of a window and select Activities
3. kwin crashes
Actual Results:  
kwin crashes and activities preferences (which windows go to which activities) get reset.

Expected Results:  
kwin should not crash and activities should not get reset

backtrace: 

Application: KWin (kwin), signal: Segmentation fault
Using host libthread_db library "/usr/lib/libthread_db.so.1".
[Current thread is 1 (Thread 0x7f15d48a3800 (LWP 22254))]

Thread 3 (Thread 0x7f15a7fff700 (LWP 22264)):
#0  0x00007f15ce086b2f in pthread_cond_wait@@GLIBC_2.3.2 () from /usr/lib/libpthread.so.0
#1  0x00007f15d32c5fab in ?? () from /usr/lib/libQtScript.so.4
#2  0x00007f15d32c5fe9 in ?? () from /usr/lib/libQtScript.so.4
#3  0x00007f15ce082124 in start_thread () from /usr/lib/libpthread.so.0
#4  0x00007f15d40c64bd in clone () from /usr/lib/libc.so.6

Thread 2 (Thread 0x7f15249d5700 (LWP 22301)):
#0  0x00007f15ce086b2f in pthread_cond_wait@@GLIBC_2.3.2 () from /usr/lib/libpthread.so.0
#1  0x00007f1526e2498b in ?? () from /usr/lib/xorg/modules/dri/r600_dri.so
#2  0x00007f1526e241b7 in ?? () from /usr/lib/xorg/modules/dri/r600_dri.so
#3  0x00007f15ce082124 in start_thread () from /usr/lib/libpthread.so.0
#4  0x00007f15d40c64bd in clone () from /usr/lib/libc.so.6

Thread 1 (Thread 0x7f15d48a3800 (LWP 22254)):
[KCrash Handler]
#5  0x00007f15cd595fb5 in QActionGroup::addAction(QAction*) () from /usr/lib/libQtGui.so.4
#6  0x00007f15d442db8f in ?? () from /usr/lib/libkdeinit4_kwin.so
#7  0x00007f15ce42a30a in QMetaObject::activate(QObject*, QMetaObject const*, int, void**) () from /usr/lib/libQtCore.so.4
#8  0x00007f15cd9c134d in QMenu::popup(QPoint const&, QAction*) () from /usr/lib/libQtGui.so.4
#9  0x00007f15cd9c298b in QMenu::internalDelayedPopup() () from /usr/lib/libQtGui.so.4
#10 0x00007f15cd9c4404 in QMenu::timerEvent(QTimerEvent*) () from /usr/lib/libQtGui.so.4
#11 0x00007f15ce42e4c1 in QObject::event(QEvent*) () from /usr/lib/libQtCore.so.4
#12 0x00007f15cd5e849b in QWidget::event(QEvent*) () from /usr/lib/libQtGui.so.4
#13 0x00007f15cd9c6aab in QMenu::event(QEvent*) () from /usr/lib/libQtGui.so.4
#14 0x00007f15cd598f0c in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib/libQtGui.so.4
#15 0x00007f15cd59f48d in QApplication::notify(QObject*, QEvent*) () from /usr/lib/libQtGui.so.4
#16 0x00007f15d2d1288a in KApplication::notify(QObject*, QEvent*) () from /usr/lib/libkdeui.so.5
#17 0x00007f15ce41658d in QCoreApplication::notifyInternal(QObject*, QEvent*) () from /usr/lib/libQtCore.so.4
#18 0x00007f15ce445d63 in ?? () from /usr/lib/libQtCore.so.4
#19 0x00007f15ce446730 in QEventDispatcherUNIX::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQtCore.so.4
#20 0x00007f15cd6368d6 in ?? () from /usr/lib/libQtGui.so.4
#21 0x00007f15ce41515f in QEventLoop::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQtCore.so.4
#22 0x00007f15ce415455 in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQtCore.so.4
#23 0x00007f15cd9c5817 in QMenu::exec(QPoint const&, QAction*) () from /usr/lib/libQtGui.so.4
#24 0x00007f15d442a10b in ?? () from /usr/lib/libkdeinit4_kwin.so
#25 0x00007f15d442a1ac in ?? () from /usr/lib/libkdeinit4_kwin.so
#26 0x00007f15d441e0a2 in ?? () from /usr/lib/libkdeinit4_kwin.so
#27 0x00007f15b57051ce in ?? () from /usr/lib/kde4/kwin3_oxygen.so
#28 0x00007f15b570fd8a in ?? () from /usr/lib/kde4/kwin3_oxygen.so
#29 0x00007f15ce4166f6 in QCoreApplicationPrivate::sendThroughObjectEventFilters(QObject*, QEvent*) () from /usr/lib/libQtCore.so.4
#30 0x00007f15cd598eec in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib/libQtGui.so.4
#31 0x00007f15cd59f5ca in QApplication::notify(QObject*, QEvent*) () from /usr/lib/libQtGui.so.4
#32 0x00007f15d2d1288a in KApplication::notify(QObject*, QEvent*) () from /usr/lib/libkdeui.so.5
#33 0x00007f15ce41658d in QCoreApplication::notifyInternal(QObject*, QEvent*) () from /usr/lib/libQtCore.so.4
#34 0x00007f15cd59edc3 in QApplicationPrivate::sendMouseEvent(QWidget*, QMouseEvent*, QWidget*, QWidget*, QWidget**, QPointer<QWidget>&, bool) () from /usr/lib/libQtGui.so.4
#35 0x00007f15cd61095b in ?? () from /usr/lib/libQtGui.so.4
#36 0x00007f15cd60f3cc in QApplication::x11ProcessEvent(_XEvent*) () from /usr/lib/libQtGui.so.4
#37 0x00007f15cd636870 in ?? () from /usr/lib/libQtGui.so.4
#38 0x00007f15ce41515f in QEventLoop::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQtCore.so.4
#39 0x00007f15ce415455 in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQtCore.so.4
#40 0x00007f15ce41a719 in QCoreApplication::exec() () from /usr/lib/libQtCore.so.4
#41 0x00007f15d4405f3e in kdemain () from /usr/lib/libkdeinit4_kwin.so
#42 0x00007f15d3ffd000 in __libc_start_main () from /usr/lib/libc.so.6
#43 0x00000000004006fe in _start ()