Application: systemsettings5 (5.2.2)

Qt Version: 5.4.1
Operating System: Linux 3.19.0-21-generic x86_64
Distribution: Ubuntu 15.04

-- Information about the crash:
I had made some settings in the compositor window but not applied tham, and pressed 'back'. I selected the option to discard changes, then this crash happened.

-- Backtrace:
Application: System Settings (systemsettings5), signal: Segmentation fault
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[Current thread is 1 (Thread 0x7f57b8ead780 (LWP 14140))]

Thread 3 (Thread 0x7f57a678b700 (LWP 14141)):
#0  0x00007f57b56288dd in poll () at ../sysdeps/unix/syscall-template.S:81
#1  0x00007f57b3942b72 in ?? () from /usr/lib/x86_64-linux-gnu/libxcb.so.1
#2  0x00007f57b394464f in xcb_wait_for_event () from /usr/lib/x86_64-linux-gnu/libxcb.so.1
#3  0x00007f57a9556099 in QXcbEventReader::run (this=0xa75190) at qxcbconnection.cpp:1105
#4  0x00007f57b5ca9b0e in QThreadPrivate::start (arg=0xa75190) at thread/qthread_unix.cpp:337
#5  0x00007f57b285c6aa in start_thread (arg=0x7f57a678b700) at pthread_create.c:333
#6  0x00007f57b5633eed in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

Thread 2 (Thread 0x7f5787105700 (LWP 14177)):
#0  0x00007f57b56288dd in poll () at ../sysdeps/unix/syscall-template.S:81
#1  0x00007f57b233debc in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#2  0x00007f57b233dfcc in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#3  0x00007f57b5f40c6c in QEventDispatcherGlib::processEvents (this=0x7f57740008c0, flags=...) at kernel/qeventdispatcher_glib.cpp:418
#4  0x00007f57b5ee53e2 in QEventLoop::exec (this=this@entry=0x7f5787104e40, flags=..., flags@entry=...) at kernel/qeventloop.cpp:204
#5  0x00007f57b5ca4b44 in QThread::exec (this=<optimized out>) at thread/qthread.cpp:503
#6  0x00007f57b5ca9b0e in QThreadPrivate::start (arg=0x1a9be50) at thread/qthread_unix.cpp:337
#7  0x00007f57b285c6aa in start_thread (arg=0x7f5787105700) at pthread_create.c:333
#8  0x00007f57b5633eed in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

Thread 1 (Thread 0x7f57b8ead780 (LWP 14140)):
[KCrash Handler]
#6  0x00007f57b4731d89 in QQuickItemPrivate::addToDirtyList() () from /usr/lib/x86_64-linux-gnu/libQt5Quick.so.5
#7  0x00007f57b4731e28 in QQuickItemPrivate::dirty(QQuickItemPrivate::DirtyType) () from /usr/lib/x86_64-linux-gnu/libQt5Quick.so.5
#8  0x00007f57b473c045 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Quick.so.5
#9  0x00007f57b5f1973a in QObject::event (this=0x27015f0, e=<optimized out>) at kernel/qobject.cpp:1245
#10 0x00007f57b473ab6b in QQuickItem::event(QEvent*) () from /usr/lib/x86_64-linux-gnu/libQt5Quick.so.5
#11 0x00007f57b6cd3b2c in QApplicationPrivate::notify_helper (this=0xa48430, receiver=0x27015f0, e=0x7f5790128710) at kernel/qapplication.cpp:3720
#12 0x00007f57b6cd9000 in QApplication::notify (this=0x7ffc97b058d0, receiver=0x27015f0, e=0x7f5790128710) at kernel/qapplication.cpp:3503
#13 0x00007f57b5ee7c2b in QCoreApplication::notifyInternal (this=0x7ffc97b058d0, receiver=0x27015f0, event=event@entry=0x7f5790128710) at kernel/qcoreapplication.cpp:935
#14 0x00007f57b5ee9c9b in sendEvent (event=0x7f5790128710, receiver=<optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:228
#15 QCoreApplicationPrivate::sendPostedEvents (receiver=receiver@entry=0x0, event_type=event_type@entry=0, data=0xa47650) at kernel/qcoreapplication.cpp:1552
#16 0x00007f57b5eea298 in QCoreApplication::sendPostedEvents (receiver=receiver@entry=0x0, event_type=event_type@entry=0) at kernel/qcoreapplication.cpp:1410
#17 0x00007f57b5f40843 in postEventSourceDispatch (s=0xab93f0) at kernel/qeventdispatcher_glib.cpp:271
#18 0x00007f57b233dc3d in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#19 0x00007f57b233df20 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#20 0x00007f57b233dfcc in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#21 0x00007f57b5f40c57 in QEventDispatcherGlib::processEvents (this=0xab9470, flags=...) at kernel/qeventdispatcher_glib.cpp:418
#22 0x00007f57b5ee53e2 in QEventLoop::exec (this=this@entry=0x7ffc97b057b0, flags=..., flags@entry=...) at kernel/qeventloop.cpp:204
#23 0x00007f57b5eed02c in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1188
#24 0x00007f57b670e31c in QGuiApplication::exec () at kernel/qguiapplication.cpp:1510
#25 0x00007f57b6ccf7a5 in QApplication::exec () at kernel/qapplication.cpp:2956
#26 0x000000000040eebc in main (argc=1, argv=<optimized out>) at ../../app/main.cpp:54

Reported using DrKonqi