Version:           r884981 (using Devel)
OS:                Linux
Installed from:    Compiled sources

Probably it is related to bug #175351.

Steps to reproduce
1) start knotes, due to bug #175351 all notes are displayed
2) hide all notes (right click on knotes in systray and select "hide all notes" action)
3) go to knotes settings
4) enable/disable "show all notes in taskbar"
5) knotes will crash:

Application: KNotes (knotes), signal SIGSEGV
0x00007f20b3a08ea0 in __nanosleep_nocancel () from /lib/libc.so.6

Thread 1 (Thread 0x7f20ba5fe750 (LWP 2736)):
[KCrash Handler]
#5  0x00007f20b47ac065 in QCoreApplication::postEvent () from /usr/lib/libQtCore.so.4
#6  0x000000000041b871 in KNotesApp::updateStyle (this=<value optimized out>) at /home/test/KDE4/src/kdepim/knotes/knotesapp.cpp:684
#7  0x000000000041e982 in KNotesApp::qt_metacall (this=0x2050a90, _c=QMetaObject::InvokeMetaMethod, _id=116, _a=0x7fffc2741c90) at /home/test/KDE4/src/build/kdepim/knotes/knotesapp.moc:130
#8  0x00007f20b47bdcf0 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#9  0x00007f20ba08ece5 in KConfigDialog::settingsChanged (this=0x259b070, _t1=<value optimized out>) at /home/test/KDE4/src/build/kdelibs/kdeui/kconfigdialog.moc:103
#10 0x00007f20ba09071c in KConfigDialog::KConfigDialogPrivate::_k_settingsChangedSlot (this=0x2ff4df0) at /home/test/KDE4/src/kdelibs/kdeui/dialogs/kconfigdialog.cpp:244
#11 0x00007f20ba090bc2 in KConfigDialog::qt_metacall (this=0x258d4c0, _c=QMetaObject::InvokeMetaMethod, _id=<value optimized out>, _a=0x7fffc2741db0)
    at /home/test/KDE4/src/build/kdelibs/kdeui/kconfigdialog.moc:86
#12 0x00000000004371bd in KNoteConfigDlg::qt_metacall (this=0x259b070, _c=58020624, _id=0, _a=0xf) at /home/test/KDE4/src/build/kdepim/knotes/knoteconfigdlg.moc:60
#13 0x00007f20b47bdcf0 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#14 0x00007f20ba092e9f in KConfigDialogManager::updateSettings (this=0x304dbb0) at /home/test/KDE4/src/kdelibs/kdeui/dialogs/kconfigdialogmanager.cpp:392
#15 0x00007f20ba093630 in KConfigDialogManager::qt_metacall (this=0x304dbb0, _c=QMetaObject::InvokeMetaMethod, _id=<value optimized out>, _a=0x7fffc2741f80)
    at /home/test/KDE4/src/build/kdelibs/kdeui/kconfigdialogmanager.moc:78
#16 0x00007f20b47bdcf0 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#17 0x00007f20ba0a2848 in KDialog::slotButtonClicked (this=0x258d4c0, button=4) at /home/test/KDE4/src/kdelibs/kdeui/dialogs/kdialog.cpp:850
#18 0x00007f20ba0a29cd in KDialog::qt_metacall (this=0x258d4c0, _c=QMetaObject::InvokeMetaMethod, _id=<value optimized out>, _a=0x7fffc27421a0)
    at /home/test/KDE4/src/build/kdelibs/kdeui/kdialog.moc:181
#19 0x00007f20ba15d9f6 in KPageDialog::qt_metacall (this=0x259b070, _c=58020624, _id=0, _a=0xf) at /home/test/KDE4/src/build/kdelibs/kdeui/kpagedialog.moc:63
#20 0x00007f20ba090b65 in KConfigDialog::qt_metacall (this=0x259b070, _c=58020624, _id=0, _a=0xf) at /home/test/KDE4/src/build/kdelibs/kdeui/kconfigdialog.moc:74
#21 0x00000000004371bd in KNoteConfigDlg::qt_metacall (this=0x259b070, _c=58020624, _id=0, _a=0xf) at /home/test/KDE4/src/build/kdepim/knotes/knoteconfigdlg.moc:60
#22 0x00007f20b47bdcf0 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#23 0x00007f20b47c224e in QSignalMapper::mapped () from /usr/lib/libQtCore.so.4
#24 0x00007f20b47c22f0 in QSignalMapper::map () from /usr/lib/libQtCore.so.4
#25 0x00007f20b47c3520 in QSignalMapper::qt_metacall () from /usr/lib/libQtCore.so.4
#26 0x00007f20b47bdcf0 in QMetaObject::activate () from /usr/lib/libQtCore.so.4
#27 0x00007f20b57e69c7 in QAbstractButton::clicked () from /usr/lib/libQtGui.so.4
#28 0x00007f20b55a6e5b in ?? () from /usr/lib/libQtGui.so.4
#29 0x00007f20b55a7c32 in ?? () from /usr/lib/libQtGui.so.4
#30 0x00007f20b55a7e65 in QAbstractButton::mouseReleaseEvent () from /usr/lib/libQtGui.so.4
#31 0x00007f20b532e59c in QWidget::event () from /usr/lib/libQtGui.so.4
#32 0x00007f20b52e14dd in QApplicationPrivate::notify_helper () from /usr/lib/libQtGui.so.4
#33 0x00007f20b52e80ee in QApplication::notify () from /usr/lib/libQtGui.so.4
#34 0x00007f20ba13178b in KApplication::notify (this=0x7fffc27438c0, receiver=0x2578440, event=0x7fffc2742c40) at /home/test/KDE4/src/kdelibs/kdeui/kernel/kapplication.cpp:307
#35 0x00007f20b47ac3c1 in QCoreApplication::notifyInternal () from /usr/lib/libQtCore.so.4
#36 0x00007f20b52e9498 in QApplicationPrivate::sendMouseEvent () from /usr/lib/libQtGui.so.4
#37 0x00007f20b533fafc in ?? () from /usr/lib/libQtGui.so.4
#38 0x00007f20b533ec79 in QApplication::x11ProcessEvent () from /usr/lib/libQtGui.so.4
#39 0x00007f20b5362724 in ?? () from /usr/lib/libQtGui.so.4
#40 0x00007f20b1006ac2 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#41 0x00007f20b100a23d in g_main_context_iterate () from /usr/lib/libglib-2.0.so.0
#42 0x00007f20b100a3fb in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#43 0x00007f20b47d088f in QEventDispatcherGlib::processEvents () from /usr/lib/libQtCore.so.4
#44 0x00007f20b5361fdf in ?? () from /usr/lib/libQtGui.so.4
#45 0x00007f20b47aad32 in QEventLoop::processEvents () from /usr/lib/libQtCore.so.4
#46 0x00007f20b47aaec5 in QEventLoop::exec () from /usr/lib/libQtCore.so.4
#47 0x00007f20b47ad015 in QCoreApplication::exec () from /usr/lib/libQtCore.so.4
#48 0x000000000041b051 in main (argc=3, argv=0x7fffc2743af8) at /home/test/KDE4/src/kdepim/knotes/main.cpp:70