backtrace of krash:
Application: Kontact (kontact), signal: Aborted
[Current thread is 1 (Thread 0x7f862f301760 (LWP 32282))]

Thread 6 (Thread 0x7f86168fc700 (LWP 32283)):
#0  0x00007f862719fe6c in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
#1  0x00007f862bb2ec12 in ?? () from /usr/lib64/libQtWebKit.so.4
#2  0x00007f862bb2ec49 in ?? () from /usr/lib64/libQtWebKit.so.4
#3  0x00007f862719bf05 in start_thread () from /lib64/libpthread.so.0
#4  0x00007f862c81e63d in clone () from /lib64/libc.so.6

Thread 5 (Thread 0x7f8615ff3700 (LWP 32284)):
#0  0x00007f862c815523 in poll () from /lib64/libc.so.6
#1  0x00007f8626c8ca98 in ?? () from /usr/lib64/libglib-2.0.so.0
#2  0x00007f8626c8cf59 in g_main_context_iteration () from /usr/lib64/libglib-2.0.so.0
#3  0x00007f862cf8c956 in QEventDispatcherGlib::processEvents (this=0x7f86100008c0, flags=<optimized out>) at kernel/qeventdispatcher_glib.cpp:426
#4  0x00007f862cf5c682 in QEventLoop::processEvents (this=<optimized out>, flags=...) at kernel/qeventloop.cpp:149
#5  0x00007f862cf5c8d7 in QEventLoop::exec (this=0x7f8615ff2e20, flags=...) at kernel/qeventloop.cpp:204
#6  0x00007f862ce5d537 in QThread::exec (this=<optimized out>) at thread/qthread.cpp:501
#7  0x00007f862ce6055b in QThreadPrivate::start (arg=0x7c0230) at thread/qthread_unix.cpp:298
#8  0x00007f862719bf05 in start_thread () from /lib64/libpthread.so.0
#9  0x00007f862c81e63d in clone () from /lib64/libc.so.6

Thread 4 (Thread 0x7f85c8914700 (LWP 32366)):
#0  0x00007f862c815523 in poll () from /lib64/libc.so.6
#1  0x00007f8626c8ca98 in ?? () from /usr/lib64/libglib-2.0.so.0
#2  0x00007f8626c8cf59 in g_main_context_iteration () from /usr/lib64/libglib-2.0.so.0
#3  0x00007f862cf8c956 in QEventDispatcherGlib::processEvents (this=0x7f85c40008c0, flags=<optimized out>) at kernel/qeventdispatcher_glib.cpp:426
#4  0x00007f862cf5c682 in QEventLoop::processEvents (this=<optimized out>, flags=...) at kernel/qeventloop.cpp:149
#5  0x00007f862cf5c8d7 in QEventLoop::exec (this=0x7f85c8913df0, flags=...) at kernel/qeventloop.cpp:204
#6  0x00007f862ce5d537 in QThread::exec (this=<optimized out>) at thread/qthread.cpp:501
#7  0x00007f862cf3c48f in QInotifyFileSystemWatcherEngine::run (this=0x185a990) at io/qfilesystemwatcher_inotify.cpp:248
#8  0x00007f862ce6055b in QThreadPrivate::start (arg=0x185a990) at thread/qthread_unix.cpp:298
#9  0x00007f862719bf05 in start_thread () from /lib64/libpthread.so.0
#10 0x00007f862c81e63d in clone () from /lib64/libc.so.6

Thread 3 (Thread 0x7f85afde8700 (LWP 599)):
#0  0x00007f862c815523 in poll () from /lib64/libc.so.6
#1  0x00007f8626c8ca98 in ?? () from /usr/lib64/libglib-2.0.so.0
#2  0x00007f8626c8cf59 in g_main_context_iteration () from /usr/lib64/libglib-2.0.so.0
#3  0x00007f862cf8c956 in QEventDispatcherGlib::processEvents (this=0x7f85a80008c0, flags=<optimized out>) at kernel/qeventdispatcher_glib.cpp:426
#4  0x00007f862cf5c682 in QEventLoop::processEvents (this=<optimized out>, flags=...) at kernel/qeventloop.cpp:149
#5  0x00007f862cf5c8d7 in QEventLoop::exec (this=0x7f85afde7e20, flags=...) at kernel/qeventloop.cpp:204
#6  0x00007f862ce5d537 in QThread::exec (this=<optimized out>) at thread/qthread.cpp:501
#7  0x00007f862ce6055b in QThreadPrivate::start (arg=0x36dbde0) at thread/qthread_unix.cpp:298
#8  0x00007f862719bf05 in start_thread () from /lib64/libpthread.so.0
#9  0x00007f862c81e63d in clone () from /lib64/libc.so.6

Thread 2 (Thread 0x7f85bee6f700 (LWP 27320)):
[KCrash Handler]
#9  0x00007f862c7b9f68 in malloc_consolidate () from /lib64/libc.so.6
#10 0x00007f862c7bb123 in _int_malloc () from /lib64/libc.so.6
#11 0x00007f862c7bdd6e in malloc () from /lib64/libc.so.6
#12 0x00007f862ce62558 in QByteArray::realloc (this=0x7f85b00239b8, alloc=65504) at tools/qbytearray.cpp:1452
#13 0x00007f862ce62679 in QByteArray::resize (this=0x7f85b00239b8, size=32768) at tools/qbytearray.cpp:1420
#14 0x00007f862813a986 in reserve (bytes=2, this=0x7f85b0022180) at ../../src/corelib/tools/qringbuffer_p.h:158
#15 QAbstractSocket::writeData (this=<optimized out>, data=0x7f85bee6e64c "\021", size=2) at socket/qabstractsocket.cpp:2315
#16 0x00007f862cef082f in QIODevice::write (this=0x7f85b00015e0, data=0x7f85bee6e64c "\021", maxSize=<optimized out>) at io/qiodevice.cpp:1370
#17 0x00007f8620461b25 in Soprano::DataStream::writeUnsignedInt16 (this=0x7f85bee6e670, v=17) at /usr/src/debug/soprano-2.7.5/server/datastream.cpp:95
#18 0x00007f8620468cba in Soprano::Client::ClientConnection::executeQuery (this=0xfc3650, modelId=223164220, query=..., type=Soprano::Query::QueryLanguageSparql, userQueryLanguage=...) at /usr/src/debug/soprano-2.7.5/client/clientconnection.cpp:263
#19 0x00007f862046a803 in Soprano::Client::ClientModel::executeQuery (this=<optimized out>, query=<optimized out>, language=<optimized out>, userQueryLanguage=<optimized out>) at /usr/src/debug/soprano-2.7.5/client/clientmodel.cpp:101
#20 0x00007f86249f464c in Nepomuk::MainModel::executeQuery (this=0xfc0e00, query=..., language=Soprano::Query::QueryLanguageSparql, userQueryLanguage=...) at /usr/src/debug/kdelibs-4.8.1/nepomuk/core/nepomukmainmodel.cpp:212
#21 0x00007f86249e0eb3 in Nepomuk::ResourceData::load (this=0x7f85b0029ba0) at /usr/src/debug/kdelibs-4.8.1/nepomuk/core/resourcedata.cpp:417
#22 0x00007f86249e17bc in Nepomuk::ResourceData::property (this=0x7f85b0029ba0, uri=...) at /usr/src/debug/kdelibs-4.8.1/nepomuk/core/resourcedata.cpp:265
#23 0x00007f86249f77e3 in Nepomuk::Resource::property (this=0x7f85bee6ed20, uri=...) at /usr/src/debug/kdelibs-4.8.1/nepomuk/core/resource.cpp:301
#24 0x00007f85cd3340ca in ?? () from /usr/lib64/libmessagecore.so.4
#25 0x00007f862ce53d12 in QThreadPoolThread::run (this=0x1297e70) at concurrent/qthreadpool.cpp:107
#26 0x00007f862ce6055b in QThreadPrivate::start (arg=0x1297e70) at thread/qthread_unix.cpp:298
#27 0x00007f862719bf05 in start_thread () from /lib64/libpthread.so.0
#28 0x00007f862c81e63d in clone () from /lib64/libc.so.6

Thread 1 (Thread 0x7f862f301760 (LWP 32282)):
[KCrash Handler]
#6  0x00007f862c779d95 in raise () from /lib64/libc.so.6
#7  0x00007f862c77b2ab in abort () from /lib64/libc.so.6
#8  0x00007f862c7b3ece in __libc_message () from /lib64/libc.so.6
#9  0x00007f862c7b9c06 in malloc_printerr () from /lib64/libc.so.6
#10 0x00007f862999554e in qMetaTypeDeleteHelper<QDBusMessage> (t=0x5222f30) at ../../src/corelib/kernel/qmetatype.h:134
#11 0x00007f862cf6dd79 in QMetaCallEvent::~QMetaCallEvent (this=0x55038d0, __in_chrg=<optimized out>) at kernel/qobject.cpp:509
#12 0x00007f862cf6ddd9 in QMetaCallEvent::~QMetaCallEvent (this=0x55038d0, __in_chrg=<optimized out>) at kernel/qobject.cpp:518
#13 0x00007f862cf61143 in QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, event_type=0, data=0x60da60) at kernel/qcoreapplication.cpp:1516
#14 0x00007f862cf8c4c3 in sendPostedEvents () at kernel/qcoreapplication.h:236
#15 postEventSourceDispatch (s=<optimized out>) at kernel/qeventdispatcher_glib.cpp:279
#16 0x00007f8626c8c58d in g_main_context_dispatch () from /usr/lib64/libglib-2.0.so.0
#17 0x00007f8626c8cd88 in ?? () from /usr/lib64/libglib-2.0.so.0
#18 0x00007f8626c8cf59 in g_main_context_iteration () from /usr/lib64/libglib-2.0.so.0
#19 0x00007f862cf8c8ef in QEventDispatcherGlib::processEvents (this=0x60d320, flags=<optimized out>) at kernel/qeventdispatcher_glib.cpp:424
#20 0x00007f862da142de in QGuiEventDispatcherGlib::processEvents (this=<optimized out>, flags=<optimized out>) at kernel/qguieventdispatcher_glib.cpp:204
#21 0x00007f862cf5c682 in QEventLoop::processEvents (this=<optimized out>, flags=...) at kernel/qeventloop.cpp:149
#22 0x00007f862cf5c8d7 in QEventLoop::exec (this=0x7fff2469a620, flags=...) at kernel/qeventloop.cpp:204
#23 0x00007f862cf61435 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1148
#24 0x0000000000403919 in ?? ()
#25 0x00007f862c76623d in __libc_start_main () from /lib64/libc.so.6
#26 0x0000000000403e51 in _start ()