(gdb) bt
#0  QDBusMetaType::typeToSignature (type=8) at qdbusmetatype.cpp:437
#1  0x00007fffe66738dc in qDBusParametersForMethod (parameterTypes=..., 
    metaTypes=..., errorMsg=...) at qdbusmisc.cpp:179
#2  0x00007fffe6673efb in qDBusParametersForMethod (mm=..., metaTypes=..., 
    errorMsg=...) at qdbusmisc.cpp:128
#3  0x00007fffe6638d9e in QDBusConnectionPrivate::findSlot (obj=obj@entry=
    0x7fffc001e0d0, normalizedName=..., params=...) at qdbusintegrator.cpp:1291
#4  0x00007fffe6639695 in QDBusConnectionPrivate::prepareHook (hook=..., 
    key=..., service=..., path=..., interface=..., name=..., argMatch=..., 
    receiver=0x7fffc001e0d0, 
    signal=0x7fffc0012a28 "2propertiesChanged(QVariantMap)", minMIdx=6, 
    buildSignature=true) at qdbusintegrator.cpp:1306
#5  0x00007fffe663a124 in QDBusConnectionPrivate::disconnectRelay (
    this=this@entry=0x7fffb40032d0, service=..., path=..., interface=..., 
    receiver=receiver@entry=0x7fffc001e0d0, signal=...)
    at qdbusintegrator.cpp:2395
#6  0x00007fffe664bca3 in QDBusAbstractInterfacePrivate::finishDisconnectNotify
    (ptr=0x7fffc001e0d0, signalId=<optimized out>)
    at qdbusabstractinterface.cpp:661
#7  0x00007fffeab5f1d9 in QObject::event (this=0x7fffc001e0d0, 
    e=<optimized out>) at kernel/qobject.cpp:1256
#8  0x00007fffeab312cb in doNotify (event=0x7fffb4021e80, 
    receiver=0x7fffc001e0d0) at kernel/qcoreapplication.cpp:1090
---Type <return> to continue, or q <return> to quit---
#9  QCoreApplication::notify (event=<optimized out>, receiver=<optimized out>, 
    this=<optimized out>) at kernel/qcoreapplication.cpp:1076
#10 QCoreApplication::notifyInternal2 (receiver=0x7fffc001e0d0, 
    event=event@entry=0x7fffb4021e80) at kernel/qcoreapplication.cpp:1015
#11 0x00007fffeab3325c in QCoreApplication::sendEvent (event=0x7fffb4021e80, 
    receiver=<optimized out>)
    at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:227
#12 QCoreApplicationPrivate::sendPostedEvents (receiver=receiver@entry=0x0, 
    event_type=event_type@entry=0, data=0x7fffbc004710)
    at kernel/qcoreapplication.cpp:1650
#13 0x00007fffeab33718 in QCoreApplication::sendPostedEvents (
    receiver=receiver@entry=0x0, event_type=event_type@entry=0)
    at kernel/qcoreapplication.cpp:1508
#14 0x00007fffeab87323 in postEventSourceDispatch (s=0x7fffc00012d0)
    at kernel/qeventdispatcher_glib.cpp:270
#15 0x00007fffe51e5dd7 in g_main_context_dispatch ()
   from /usr/lib/libglib-2.0.so.0
#16 0x00007fffe51e6040 in ?? () from /usr/lib/libglib-2.0.so.0
#17 0x00007fffe51e60ec in g_main_context_iteration ()
   from /usr/lib/libglib-2.0.so.0
#18 0x00007fffeab8772f in QEventDispatcherGlib::processEvents (
    this=0x7fffc00008c0, flags=...) at kernel/qeventdispatcher_glib.cpp:417
#19 0x00007fffeab2f4ca in QEventLoop::exec (this=this@entry=0x7fffcaffcdc0, 
---Type <return> to continue, or q <return> to quit---
    flags=..., flags@entry=...) at kernel/qeventloop.cpp:204
#20 0x00007fffea9562f3 in QThread::exec (this=<optimized out>)
    at thread/qthread.cpp:503
#21 0x00007fffea95b1d8 in QThreadPrivate::start (arg=0x7fffbc0044f0)
    at thread/qthread_unix.cpp:340
#22 0x00007fffec9ea474 in start_thread () from /usr/lib/libpthread.so.0
#23 0x00007fffe9d5569d in clone () from /usr/lib/libc.so.6