KDialog crashes if it is given no, or unknown, command line options. The backtrace is:

Application: kdialog (kdialog), signal: Segmentation fault
Using host libthread_db library "/usr/lib/libthread_db.so.1".
[Current thread is 1 (Thread 0x7f4892ebf000 (LWP 27369))]

Thread 2 (Thread 0x7f487ea0c700 (LWP 27370)):
#0  0x00007f488ea4567d in poll () from /usr/lib/libc.so.6
#1  0x00007f488b5268e0 in ?? () from /usr/lib/libxcb.so.1
#2  0x00007f488b528679 in xcb_wait_for_event () from /usr/lib/libxcb.so.1
#3  0x00007f4880d679e9 in QXcbEventReader::run (this=0x846f80) at qxcbconnection.cpp:1345
#4  0x00007f488f13e6b8 in QThreadPrivate::start (arg=0x846f80) at thread/qthread_unix.cpp:368
#5  0x00007f48898fe2e7 in start_thread () from /usr/lib/libpthread.so.0
#6  0x00007f488ea4f54f in clone () from /usr/lib/libc.so.6

Thread 1 (Thread 0x7f4892ebf000 (LWP 27369)):
[KCrash Handler]
#6  std::__atomic_base<QMutexData*>::compare_exchange_strong (__m2=std::memory_order_acquire, __m1=std::memory_order_acquire, __p2=<optimized out>, __p1=@0x7fff386a0218: 0x0, this=0x20) at /usr/include/c++/6.3.1/bits/atomic_base.h:752
#7  std::atomic<QMutexData*>::compare_exchange_strong (__m2=std::memory_order_acquire, __m1=std::memory_order_acquire, __p2=<optimized out>, __p1=@0x7fff386a0218: 0x0, this=0x20) at /usr/include/c++/6.3.1/atomic:466
#8  QAtomicOps<QMutexData*>::testAndSetAcquire<QMutexData*> (currentValue=<synthetic pointer>, newValue=<optimized out>, expectedValue=0x0, _q_value=...) at ../../include/QtCore/../../src/corelib/arch/qatomic_cxx11.h:290
#9  QBasicAtomicPointer<QMutexData>::testAndSetAcquire (currentValue=<synthetic pointer>: <optimized out>, newValue=<optimized out>, expectedValue=0x0, this=0x20) at ../../include/QtCore/../../src/corelib/thread/qbasicatomic.h:262
#10 QBasicMutex::fastTryLock (current=<synthetic pointer>: <optimized out>, this=0x20) at thread/qmutex.h:101
#11 QMutex::lock (this=this@entry=0x20) at thread/qmutex.cpp:224
#12 0x00007f4890e59ab7 in QMutexLocker::QMutexLocker (m=0x20, this=<synthetic pointer>) at ../../include/QtCore/../../src/corelib/thread/qmutex.h:199
#13 QDBusConnectionManager::busConnection (this=0x0, type=type@entry=QDBusConnection::SessionBus) at qdbusconnection.cpp:105
#14 0x00007f4890e5ab7c in QDBusConnection::sessionBus () at qdbusconnection.cpp:1169
#15 0x00007f487ca23956 in QtCurve::Style::disconnectDBus() () from /usr/lib/qt/plugins/styles/qtcurve.so
#16 0x00007f487ca61236 in QtCurve::StylePlugin::~StylePlugin() () from /usr/lib/qt/plugins/styles/qtcurve.so
#17 0x00007f488f30d5b9 in QLibraryPrivate::unload (this=this@entry=0x88a470, flag=flag@entry=QLibraryPrivate::UnloadSys) at plugin/qlibrary.cpp:562
#18 0x00007f488f303252 in QFactoryLoaderPrivate::~QFactoryLoaderPrivate (this=0x8898a0, __in_chrg=<optimized out>) at plugin/qfactoryloader.cpp:86
#19 0x00007f488f303379 in QFactoryLoaderPrivate::~QFactoryLoaderPrivate (this=0x8898a0, __in_chrg=<optimized out>) at plugin/qfactoryloader.cpp:89
#20 0x00007f488f34bfd7 in QScopedPointerDeleter<QObjectData>::cleanup (pointer=<optimized out>) at ../../include/QtCore/../../src/corelib/tools/qscopedpointer.h:60
#21 QScopedPointer<QObjectData, QScopedPointerDeleter<QObjectData> >::~QScopedPointer (this=0x7f4890706858 <(anonymous namespace)::Q_QGS_loader::innerFunction()::holder+8>, __in_chrg=<optimized out>) at ../../include/QtCore/../../src/corelib/tools/qscopedpointer.h:107
#22 QObject::~QObject (this=<optimized out>, __in_chrg=<optimized out>) at kernel/qobject.cpp:900
#23 0x00007f488f3027ae in QFactoryLoader::~QFactoryLoader (this=0x7f4890706850 <(anonymous namespace)::Q_QGS_loader::innerFunction()::holder>, __in_chrg=<optimized out>) at plugin/qfactoryloader.cpp:211
#24 0x00007f4890072389 in (anonymous namespace)::Q_QGS_loader::Holder::~Holder (this=<optimized out>, __in_chrg=<optimized out>) at styles/qstylefactory.cpp:66
#25 0x00007f488e9996c0 in __run_exit_handlers () from /usr/lib/libc.so.6
#26 0x00007f488e99971a in exit () from /usr/lib/libc.so.6
#27 0x00007f488f1f7354 in QCommandLineParser::showHelp (this=<optimized out>, exitCode=0) at tools/qcommandlineparser.cpp:1036
#28 0x000000000040fcfa in ?? ()
#29 0x00007f488e983511 in __libc_start_main () from /usr/lib/libc.so.6
#30 0x00000000004100fa in _start ()