Application that crashed: kontact
Version of the application: 4.3.2
KDE Version: 4.3.2 (KDE 4.3.2)
Qt Version: 4.5.3
Operating System: Linux 2.6.30-gentoo-r5 x86_64

What I was doing when the application crashed:
I selected a folder with many emails and entered words in the search bar before any mails were shown. 

Kontact crashed before showing any results. 

 -- Backtrace:
Application: Kontact (kontact), signal: Aborted
[KCrash Handler]
#33 0x00007fa8534af205 in raise () from /lib/libc.so.6
#34 0x00007fa8534b0723 in abort () from /lib/libc.so.6
#35 0x00007fa8541e7295 in qt_message_output (msgType=QtFatalMsg, buf=<value optimized out>) at global/qglobal.cpp:2042
#36 0x00007fa8541e73b0 in qFatal (msg=<value optimized out>) at global/qglobal.cpp:2241
#37 0x00007fa842c10d23 in KMail::MessageListView::Core::Model::applyFilterToSubtree (this=0x14ce740, item=0x42a94b0, parentIndex=@0x7fffd7828180)
    at /var/tmp/portage/kde-base/kmail-4.3.2/work/kmail-4.3.2/kmail/messagelistview/core/model.cpp:348
#38 0x00007fa842c1702e in KMail::MessageListView::Core::Model::setFilter (this=0x14ce740, filter=<value optimized out>)
    at /var/tmp/portage/kde-base/kmail-4.3.2/work/kmail-4.3.2/kmail/messagelistview/core/model.cpp:340
#39 0x00007fa842c3f08c in KMail::MessageListView::Core::Widget::searchTimerFired (this=0x147df80)
    at /var/tmp/portage/kde-base/kmail-4.3.2/work/kmail-4.3.2/kmail/messagelistview/core/widgetbase.cpp:1130
#40 0x00007fa842906963 in KMail::MessageListView::Core::Widget::qt_metacall (this=0x147df80, _c=QMetaObject::InvokeMetaMethod, _id=<value optimized out>, _a=0x7fffd7828320)
    at /var/tmp/portage/kde-base/kmail-4.3.2/work/kmail-4.3.2_build/kmail/moc_widgetbase.cpp:119
#41 0x00007fa842906a75 in KMail::MessageListView::Widget::qt_metacall (this=0x66a4, _c=26276, _id=6, _a=0xffffffffffffffff)
    at /var/tmp/portage/kde-base/kmail-4.3.2/work/kmail-4.3.2_build/kmail/moc_widget.cpp:75
#42 0x00007fa8542e1eb9 in QMetaObject::activate (sender=0x64e6670, from_signal_index=<value optimized out>, to_signal_index=4, argv=0xffffffffffffffff) at kernel/qobject.cpp:3101
#43 0x00007fa8542dc7b3 in QObject::event (this=0x64e6670, e=0x66a4) at kernel/qobject.cpp:1066
#44 0x00007fa8550716dd in QApplicationPrivate::notify_helper (this=0x64a530, receiver=0x64e6670, e=0x7fffd78289f0) at kernel/qapplication.cpp:4065
#45 0x00007fa85507a00e in QApplication::notify (this=0x7fffd7828d30, receiver=0x64e6670, e=0x7fffd78289f0) at kernel/qapplication.cpp:4030
#46 0x00007fa855e41341 in KApplication::notify (this=0x7fffd7828d30, receiver=0x64e6670, event=0x7fffd78289f0)
    at /var/tmp/portage/kde-base/kdelibs-4.3.2-r2/work/kdelibs-4.3.2/kdeui/kernel/kapplication.cpp:302
#47 0x00007fa8542ccd53 in QCoreApplication::notifyInternal (this=0x7fffd7828d30, receiver=0x64e6670, event=0x7fffd78289f0) at kernel/qcoreapplication.cpp:606
#48 0x00007fa8542f6c46 in QTimerInfoList::activateTimers (this=0x63ceb0) at kernel/qcoreapplication.h:213
#49 0x00007fa8542f3e7d in timerSourceDispatch (source=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:165
#50 0x00007fa84f8acf41 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#51 0x00007fa84f8b04d8 in g_main_context_iterate () from /usr/lib/libglib-2.0.so.0
#52 0x00007fa84f8b068c in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#53 0x00007fa8542f3def in QEventDispatcherGlib::processEvents (this=0x634770, flags=<value optimized out>) at kernel/qeventdispatcher_glib.cpp:328
#54 0x00007fa8550fd28f in QGuiEventDispatcherGlib::processEvents (this=0x66a4, flags=<value optimized out>) at kernel/qguieventdispatcher_glib.cpp:202
#55 0x00007fa8542cba12 in QEventLoop::processEvents (this=<value optimized out>, flags={i = -679310240}) at kernel/qeventloop.cpp:149
#56 0x00007fa8542cbbac in QEventLoop::exec (this=0x7fffd7828ca0, flags={i = -679310160}) at kernel/qeventloop.cpp:197
#57 0x00007fa8542d0526 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:888
#58 0x000000000040405a in main (argc=1, argv=0x7fffd7829248) at /var/tmp/portage/kde-base/kontact-4.3.2/work/kontact-4.3.2/kontact/src/main.cpp:218

Reported using DrKonqi