Application: kmail (5.3.0 (QtWebEngine))

Qt Version: 5.7.0
Frameworks Version: 5.27.0
Operating System: Linux 4.8.4-1-ck x86_64
Distribution (Platform): Archlinux Packages

-- Information about the crash:
- What I was doing when the application crashed:
closed KMail

- Custom settings of the application:

Use plasma with arc-dark and kvantum theme engine. This error only occours if i use kvantum

The crash can be reproduced every time.

-- Backtrace:
Application: KMail (kmail), signal: Segmentation fault
Using host libthread_db library "/usr/lib/libthread_db.so.1".
[Current thread is 1 (Thread 0x7fd3dcdce580 (LWP 28964))]

Thread 3 (Thread 0x7fd379fbe700 (LWP 29006)):
#0  0x00007fd3cf84c10f in pthread_cond_wait@@GLIBC_2.3.2 () at /usr/lib/libpthread.so.0
#1  0x00007fd3c564ec35 in  () at /usr/lib/libQt5WebEngineCore.so.5
#2  0x00007fd3c564ed05 in  () at /usr/lib/libQt5WebEngineCore.so.5
#3  0x00007fd3c562fd03 in  () at /usr/lib/libQt5WebEngineCore.so.5
#4  0x00007fd3c5641f54 in  () at /usr/lib/libQt5WebEngineCore.so.5
#5  0x00007fd3c562bee5 in  () at /usr/lib/libQt5WebEngineCore.so.5
#6  0x00007fd3c565ad6a in  () at /usr/lib/libQt5WebEngineCore.so.5
#7  0x00007fd3c56570dc in  () at /usr/lib/libQt5WebEngineCore.so.5
#8  0x00007fd3cf846454 in start_thread () at /usr/lib/libpthread.so.0
#9  0x00007fd3d9c6f7df in clone () at /usr/lib/libc.so.6

Thread 2 (Thread 0x7fd39ddee700 (LWP 28989)):
#0  0x00007fd3d9c6648d in poll () at /usr/lib/libc.so.6
#1  0x00007fd3cdca1786 in  () at /usr/lib/libglib-2.0.so.0
#2  0x00007fd3cdca189c in g_main_context_iteration () at /usr/lib/libglib-2.0.so.0
#3  0x00007fd3da7a272b in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/libQt5Core.so.5
#4  0x00007fd3da74c23a in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/libQt5Core.so.5
#5  0x00007fd3da56f0f3 in QThread::exec() () at /usr/lib/libQt5Core.so.5
#6  0x00007fd3d8b84e55 in  () at /usr/lib/libQt5DBus.so.5
#7  0x00007fd3da573d78 in  () at /usr/lib/libQt5Core.so.5
#8  0x00007fd3cf846454 in start_thread () at /usr/lib/libpthread.so.0
#9  0x00007fd3d9c6f7df in clone () at /usr/lib/libc.so.6

Thread 1 (Thread 0x7fd3dcdce580 (LWP 28964)):
[KCrash Handler]
#6  0x00007fd3daca79c2 in QWindow::destroy() () at /usr/lib/libQt5Gui.so.5
#7  0x00007fd3db46a0f7 in QWidgetPrivate::deleteTLSysExtra() () at /usr/lib/libQt5Widgets.so.5
#8  0x00007fd3db46efb0 in QWidget::destroy(bool, bool) () at /usr/lib/libQt5Widgets.so.5
#9  0x00007fd3db4758b7 in QWidget::~QWidget() () at /usr/lib/libQt5Widgets.so.5
#10 0x00007fd3db565379 in QLabel::~QLabel() () at /usr/lib/libQt5Widgets.so.5
#11 0x00007fd3d08fa545 in  () at /usr/lib/libQt5WebEngineWidgets.so.5
#12 0x00007fd3d08fa579 in  () at /usr/lib/libQt5WebEngineWidgets.so.5
#13 0x00007fd3d9bbc990 in __run_exit_handlers () at /usr/lib/libc.so.6
#14 0x00007fd3d9bbc9ea in  () at /usr/lib/libc.so.6
#15 0x00007fd3d9ba7298 in __libc_start_main () at /usr/lib/libc.so.6
#16 0x000000000040403a in _start ()

Reported using DrKonqi