It only happens if you build Qt in debug mode. Packaged Qt is built in release mode, where all Q_ASSERT* are NOOPS.
This is the error message:
ASSERT failure in QDBusAbstractInterface: "Interface name cannot be empty", file /home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/src/dbus/qdbusabstractinterface.cpp, line 88
And this is the stack trace:
#0 0x00007f1ecbf98418 in __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:54
#1 0x00007f1ecbf9a01a in __GI_abort () at abort.c:89
#2 0x00007f1ecc970b17 in qt_message_fatal (context=..., message=...) at /home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/src/corelib/global/qlogging.cpp:1648
#3 0x00007f1ecc96cb6a in QMessageLogger::fatal (this=0x7f1e7b821e10, msg=0x7f1eccccbd98 "ASSERT failure in %s: \"%s\", file %s, line %d") at /home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/src/corelib/global/qlogging.cpp:790
#4 0x00007f1ecc965361 in qt_assert_x (where=0x7f1eceb6b4be "QDBusAbstractInterface", what=0x7f1eceb6b3b8 "Interface name cannot be empty", file=0x7f1eceb6b460 "/home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/src/dbus/qdbusabstractinterface.cpp", line=88)
at /home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/src/corelib/global/qglobal.cpp:3007
#5 0x00007f1eceb25f2e in checkIfValid (service=..., path=..., interface=..., isDynamic=false, isPeer=false) at /home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/src/dbus/qdbusabstractinterface.cpp:88
#6 0x00007f1eceb26143 in QDBusAbstractInterfacePrivate::QDBusAbstractInterfacePrivate (this=0x7f1e74003860, serv=..., p=..., iface=..., con=..., isDynamic=false) at /home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/src/dbus/qdbusabstractinterface.cpp:110
#7 0x00007f1eceb2761e in QDBusAbstractInterface::QDBusAbstractInterface (this=0x7f1e74003720, service=..., path=..., interface=0x7f1e74003068 "", con=..., parent=0x0) at /home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/src/dbus/qdbusabstractinterface.cpp:334
#8 0x00007f1e869fc343 in AsyncDBusInterface::AsyncDBusInterface (this=0x7f1e74003720, service=..., path=..., interface=..., connection=..., parent=0x0) at /home/dandrader/unity8/miral/plugins/Unity/DashCommunicator/dashconnection.cpp:39
#9 0x00007f1e869fbe80 in DashConnection::createInterface (this=0x7f1e74002d90, service=..., path=..., interface=..., connection=...) at /home/dandrader/unity8/miral/plugins/Unity/DashCommunicator/dashconnection.cpp:55
#10 0x00007f1eac1b1881 in AbstractDBusServiceMonitor::onServiceRegistered (this=0x7f1e74002d90) at /home/dandrader/unity8/miral/src/libunity8-private/abstractdbusservicemonitor.cpp:65
#11 0x00007f1eac1b2074 in QtPrivate::FunctorCall<QtPrivate::IndexesList<0>, QtPrivate::List<QString const&>, void, void (AbstractDBusServiceMonitor::*)(QString const&)>::call (f=
(void (AbstractDBusServiceMonitor::*)(AbstractDBusServiceMonitor * const, const QString &)) 0x7f1eac1b17c0 <AbstractDBusServiceMonitor::onServiceRegistered(QString const&)>, o=0x7f1e74002d90, arg=0x7f1e7b8222d0) at /usr/include/x86_64-linux-gnu/qt5/QtCore/qobjectdefs_impl.h:501
#12 0x00007f1eac1b1fe9 in QtPrivate::FunctionPointer<void (AbstractDBusServiceMonitor::*)(QString const&)>::call<QtPrivate::List<QString const&>, void> (f=
(void (AbstractDBusServiceMonitor::*)(AbstractDBusServiceMonitor * const, const QString &)) 0x7f1eac1b17c0 <AbstractDBusServiceMonitor::onServiceRegistered(QString const&)>, o=0x7f1e74002d90, arg=0x7f1e7b8222d0) at /usr/include/x86_64-linux-gnu/qt5/QtCore/qobjectdefs_impl.h:520
#13 0x00007f1eac1b1f53 in QtPrivate::QSlotObject<void (AbstractDBusServiceMonitor::*)(QString const&), QtPrivate::List<QString const&>, void>::impl (which=1, this_=0x7f1e74002ff0, r=0x7f1e74002d90, a=0x7f1e7b8222d0, ret=0x0) at /usr/include/x86_64-linux-gnu/qt5/QtCore/qobject_impl.h:143
#14 0x00007f1eccc1d681 in QtPrivate::QSlotObjectBase::call (this=0x7f1e74002ff0, r=0x7f1e74002d90, a=0x7f1e7b8222d0) at /home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/include/QtCore/../../src/corelib/kernel/qobject_impl.h:124
#15 0x00007f1eccc1a3b8 in QMetaObject::activate (sender=0x7f1e740013a0, signalOffset=3, local_signal_index=0, argv=0x7f1e7b8222d0) at /home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/src/corelib/kernel/qobject.cpp:3715
#16 0x00007f1eccc19cac in QMetaObject::activate (sender=0x7f1e740013a0, m=0x7f1eceb9e600 <QDBusServiceWatcher::staticMetaObject>, local_signal_index=0, argv=0x7f1e7b8222d0) at /home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/src/corelib/kernel/qobject.cpp:3595
#17 0x00007f1eceb62ce2 in QDBusServiceWatcher::serviceRegistered (this=0x7f1e740013a0, _t1=...) at .moc/moc_qdbusservicewatcher.cpp:208
#18 0x00007f1eceb61f89 in QDBusServiceWatcherPrivate::_q_serviceOwnerChanged (this=0x7f1e74002e60, service=..., oldOwner=..., newOwner=...) at /home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/src/dbus/qdbusservicewatcher.cpp:72
#19 0x00007f1eceb6292c in QDBusServiceWatcher::qt_static_metacall (_o=0x7f1e740013a0, _c=QMetaObject::InvokeMetaMethod, _id=3, _a=0x7f1e7b822520) at .moc/moc_qdbusservicewatcher.cpp:99
#20 0x00007f1eceb62bf1 in QDBusServiceWatcher::qt_metacall (this=0x7f1e740013a0, _c=QMetaObject::InvokeMetaMethod, _id=3, _a=0x7f1e7b822520) at .moc/moc_qdbusservicewatcher.cpp:177
#21 0x00007f1eceb093a1 in QDBusConnectionPrivate::deliverCall (this=0x7f1e8c0113c0, object=0x7f1e740013a0, msg=..., metaTypes=..., slotIdx=8) at /home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/src/dbus/qdbusintegrator.cpp:990
#22 0x00007f1eceb142f7 in QDBusCallDeliveryEvent::placeMetaCall (this=0x7f1e8c016c00, object=0x7f1e740013a0) at /home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/src/dbus/qdbusintegrator_p.h:107
#23 0x00007f1eccc135d1 in QObject::event (this=0x7f1e740013a0, e=0x7f1e8c016c00) at /home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/src/corelib/kernel/qobject.cpp:1256
#24 0x00007f1eccbd59d0 in QCoreApplicationPrivate::notify_helper (receiver=0x7f1e740013a0, event=0x7f1e8c016c00) at /home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/src/corelib/kernel/qcoreapplication.cpp:1149
#25 0x00007f1eccbd55fa in doNotify (receiver=0x7f1e740013a0, event=0x7f1e8c016c00) at /home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/src/corelib/kernel/qcoreapplication.cpp:1090
#26 0x00007f1eccbd555e in QCoreApplication::notify (this=0x2130880, receiver=0x7f1e740013a0, event=0x7f1e8c016c00) at /home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/src/corelib/kernel/qcoreapplication.cpp:1076
#27 0x00007f1ecd5f9976 in QGuiApplication::notify (this=0x2130880, object=0x7f1e740013a0, event=0x7f1e8c016c00) at /home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/src/gui/kernel/qguiapplication.cpp:1611
#28 0x00007f1eccbd54db in QCoreApplication::notifyInternal2 (receiver=0x7f1e740013a0, event=0x7f1e8c016c00) at /home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/src/corelib/kernel/qcoreapplication.cpp:1015
#29 0x00007f1eccbd97c4 in QCoreApplication::sendEvent (receiver=0x7f1e740013a0, event=0x7f1e8c016c00) at /home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/src/corelib/kernel/qcoreapplication.h:225
#30 0x00007f1eccbd697b in QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, event_type=0, data=0x2311b00) at /home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/src/corelib/kernel/qcoreapplication.cpp:1650
#31 0x00007f1eccbd62e0 in QCoreApplication::sendPostedEvents (receiver=0x0, event_type=0) at /home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/src/corelib/kernel/qcoreapplication.cpp:1508
#32 0x00007f1eccc590db in postEventSourceDispatch (s=0x7f1e740012d0) at /home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/src/corelib/kernel/qeventdispatcher_glib.cpp:270
#33 0x00007f1ec97561a7 in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#34 0x00007f1ec9756400 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#35 0x00007f1ec97564ac in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#36 0x00007f1eccc59915 in QEventDispatcherGlib::processEvents (this=0x7f1e740008c0, flags=...) at /home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/src/corelib/kernel/qeventdispatcher_glib.cpp:419
#37 0x00007f1eccbd1b26 in QEventLoop::processEvents (this=0x7f1e7b822c40, flags=...) at /home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/src/corelib/kernel/qeventloop.cpp:128
#38 0x00007f1eccbd1e5d in QEventLoop::exec (this=0x7f1e7b822c40, flags=...) at /home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/src/corelib/kernel/qeventloop.cpp:204
#39 0x00007f1ecc97f459 in QThread::exec (this=0x2310410) at /home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/src/corelib/thread/qthread.cpp:500
#40 0x00007f1e869fbb3a in DashCommunicator::run (this=0x2310410) at /home/dandrader/unity8/miral/plugins/Unity/DashCommunicator/dashcommunicator.cpp:57
#41 0x00007f1ecc987e0c in QThreadPrivate::start (arg=0x2310410) at /home/dandrader/packages/qtbase-opensource-src-5.6.1+dfsg/src/corelib/thread/qthread_unix.cpp:341
#42 0x00007f1ecbd4d6fa in start_thread (arg=0x7f1e7b823700) at pthread_create.c:333
#43 0x00007f1ecc069b5d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109
