I compiled and installed recent git snapshots of libkscreen and kscreen. Afterwards, i executed:

qdbus org.kde.kded /kded org.kde.kded.unloadModule randrmonitor
qdbus org.kde.kded /kded org.kde.kded.setModuleAutoloading randrmonitor false
qdbus org.kde.kded /kded org.kde.kded.loadModule kscreen

Now kded crashes upon each KDE startup with the following backtrace whereas thread 1 points to kscreen:

----------------------------------
Application: KDE-Dienst (kdeinit4), signal: Segmentation fault
Using host libthread_db library "/lib64/libthread_db.so.1".
[Current thread is 1 (Thread 0x7f218c35a780 (LWP 8090))]

Thread 3 (Thread 0x7f216fc17700 (LWP 8099)):
#0  0x00007f218ac28dc5 in pthread_mutex_lock () from /lib64/libpthread.so.0
#1  0x00007f218671e471 in g_mutex_lock () from /usr/lib64/libglib-2.0.so.0
#2  0x00007f21866e1f9b in g_main_context_query () from /usr/lib64/libglib-2.0.so.0
#3  0x00007f21866e25f9 in ?? () from /usr/lib64/libglib-2.0.so.0
#4  0x00007f21866e27a4 in g_main_context_iteration () from /usr/lib64/libglib-2.0.so.0
#5  0x00007f218afe7136 in QEventDispatcherGlib::processEvents (this=0x7f21680008c0, flags=...) at kernel/qeventdispatcher_glib.cpp:426
#6  0x00007f218afb794f in QEventLoop::processEvents (this=this@entry=0x7f216fc16dd0, flags=...) at kernel/qeventloop.cpp:149
#7  0x00007f218afb7bd8 in QEventLoop::exec (this=0x7f216fc16dd0, flags=...) at kernel/qeventloop.cpp:204
#8  0x00007f218aeba0b0 in QThread::exec (this=<optimized out>) at thread/qthread.cpp:542
#9  0x00007f218af980bf in QInotifyFileSystemWatcherEngine::run (this=0x2316da0) at io/qfilesystemwatcher_inotify.cpp:256
#10 0x00007f218aebd08c in QThreadPrivate::start (arg=0x2316da0) at thread/qthread_unix.cpp:338
#11 0x00007f218ac26e0e in start_thread () from /lib64/libpthread.so.0
#12 0x00007f21899a02cd in clone () from /lib64/libc.so.6

Thread 2 (Thread 0x7f2167fff700 (LWP 8110)):
#0  0x00007f218999814f in poll () from /lib64/libc.so.6
#1  0x00007f21866e2684 in ?? () from /usr/lib64/libglib-2.0.so.0
#2  0x00007f21866e2ae2 in g_main_loop_run () from /usr/lib64/libglib-2.0.so.0
#3  0x00007f216c6b1a26 in ?? () from /usr/lib64/libgio-2.0.so.0
#4  0x00007f21867050e5 in ?? () from /usr/lib64/libglib-2.0.so.0
#5  0x00007f218ac26e0e in start_thread () from /lib64/libpthread.so.0
#6  0x00007f21899a02cd in clone () from /lib64/libc.so.6

Thread 1 (Thread 0x7f218c35a780 (LWP 8090)):
[KCrash Handler]
#6  KScreen::Edid::hash (this=0x0) at /home/ademmer/Source/other/libkscreen/src/edid.cpp:132
#7  0x00007f2172a23123 in Serializer::currentId () at /home/ademmer/Source/other/kscreen/kded/serializer.cpp:46
#8  0x00007f2172a231ee in Serializer::configExists () at /home/ademmer/Source/other/kscreen/kded/serializer.cpp:58
#9  0x00007f2172a21b3c in KScreenDaemon::applyConfig (this=this@entry=0x22f9b70) at /home/ademmer/Source/other/kscreen/kded/daemon.cpp:76
#10 0x00007f2172a22939 in KScreenDaemon::init (this=0x22f9b70) at /home/ademmer/Source/other/kscreen/kded/daemon.cpp:68
#11 0x00007f218afce0ff in QMetaObject::activate (sender=0x241f610, m=<optimized out>, local_signal_index=<optimized out>, argv=0x0) at kernel/qobject.cpp:3548
#12 0x00007f218afce0ff in QMetaObject::activate (sender=0x2428a20, m=<optimized out>, local_signal_index=<optimized out>, argv=0x0) at kernel/qobject.cpp:3548
#13 0x00007f2172a2a60f in fetchIsDocked (this=0x2428a20) at /home/ademmer/Source/other/kscreen/kded/device.cpp:151
#14 Device::isLidClosedFetched (this=0x2428a20, watcher=0x25c57f0) at /home/ademmer/Source/other/kscreen/kded/device.cpp:146
#15 0x00007f218afce0ff in QMetaObject::activate (sender=0x25c57f0, m=<optimized out>, local_signal_index=<optimized out>, argv=0x7ffff57b0ed0) at kernel/qobject.cpp:3548
#16 0x00007f2187d7a16f in QDBusPendingCallWatcher::finished (this=<optimized out>, _t1=0x25c57f0) at .moc/release-shared/moc_qdbuspendingcall.cpp:106
#17 0x00007f218afcd5de in QObject::event (this=0x25c57f0, e=<optimized out>) at kernel/qobject.cpp:1203
#18 0x00007f218a14685c in QApplicationPrivate::notify_helper (this=this@entry=0x21a5520, receiver=receiver@entry=0x25c57f0, e=e@entry=0x25b8110) at kernel/qapplication.cpp:4562
#19 0x00007f218a14acda in QApplication::notify (this=0x7ffff57b2b00, receiver=0x25c57f0, e=0x25b8110) at kernel/qapplication.cpp:4423
#20 0x00007f218bd5aa86 in KApplication::notify (this=0x7ffff57b2b00, receiver=0x25c57f0, event=0x25b8110) at /usr/src/debug/kdelibs-4.9.95/kdeui/kernel/kapplication.cpp:311
#21 0x00007f218afb8bfe in QCoreApplication::notifyInternal (this=0x7ffff57b2b00, receiver=receiver@entry=0x25c57f0, event=event@entry=0x25b8110) at kernel/qcoreapplication.cpp:946
#22 0x00007f218afbc561 in sendEvent (event=0x25b8110, receiver=0x25c57f0) at kernel/qcoreapplication.h:231
#23 QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, event_type=0, data=0x21172b0) at kernel/qcoreapplication.cpp:1570
#24 0x00007f218afe6f83 in sendPostedEvents () at kernel/qcoreapplication.h:236
#25 postEventSourceDispatch (s=0x21a6700) at kernel/qeventdispatcher_glib.cpp:279
#26 0x00007f21866e23b5 in g_main_context_dispatch () from /usr/lib64/libglib-2.0.so.0
#27 0x00007f21866e26e8 in ?? () from /usr/lib64/libglib-2.0.so.0
#28 0x00007f21866e27a4 in g_main_context_iteration () from /usr/lib64/libglib-2.0.so.0
#29 0x00007f218afe7116 in QEventDispatcherGlib::processEvents (this=0x211d790, flags=...) at kernel/qeventdispatcher_glib.cpp:424
#30 0x00007f218a1e6bee in QGuiEventDispatcherGlib::processEvents (this=<optimized out>, flags=...) at kernel/qguieventdispatcher_glib.cpp:204
#31 0x00007f218afb794f in QEventLoop::processEvents (this=this@entry=0x7ffff57b17e0, flags=...) at kernel/qeventloop.cpp:149
#32 0x00007f218afb7bd8 in QEventLoop::exec (this=0x7ffff57b17e0, flags=...) at kernel/qeventloop.cpp:204
#33 0x00007f216cd6f323 in KAuth::Polkit1Backend::actionExists (this=0x23a63a0, action=...) at /usr/src/debug/kdelibs-4.9.95/kdecore/auth/backends/polkit-1/Polkit1Backend.cpp:219
#34 0x00007f218b4719d8 in setName (name=..., this=<optimized out>) at /usr/src/debug/kdelibs-4.9.95/kdecore/auth/kauthaction.cpp:110
#35 KAuth::Action::setName (this=<optimized out>, name=...) at /usr/src/debug/kdelibs-4.9.95/kdecore/auth/kauthaction.cpp:103
#36 0x00007f218b471a5a in KAuth::Action::Action (this=0x7ffff57b18b0, name=...) at /usr/src/debug/kdelibs-4.9.95/kdecore/auth/kauthaction.cpp:61
#37 0x00007f2173dd2f4e in PowerDevilUPowerBackend::brightness (this=0x23a4850, type=<optimized out>) at /home/ademmer/Source/own/KDE/kde-workspace/powerdevil/daemon/backends/upower/powerdevilupowerbackend.cpp:189
#38 0x00007f2173dd5486 in PowerDevilUPowerBackend::init (this=0x23a4850) at /home/ademmer/Source/own/KDE/kde-workspace/powerdevil/daemon/backends/upower/powerdevilupowerbackend.cpp:110
#39 0x00007f2173541841 in PowerDevil::Core::loadCore (this=0x2395cc0, backend=<optimized out>) at /home/ademmer/Source/own/KDE/kde-workspace/powerdevil/daemon/powerdevilcore.cpp:84
#40 0x00007f2173dceb43 in KDEDPowerDevil::init (this=0x219bca0) at /home/ademmer/Source/own/KDE/kde-workspace/powerdevil/daemon/kdedpowerdevil.cpp:89
#41 0x00007f218afcd5de in QObject::event (this=0x219bca0, e=<optimized out>) at kernel/qobject.cpp:1203
#42 0x00007f218a14685c in QApplicationPrivate::notify_helper (this=this@entry=0x21a5520, receiver=receiver@entry=0x219bca0, e=e@entry=0x22fea60) at kernel/qapplication.cpp:4562
#43 0x00007f218a14acda in QApplication::notify (this=0x7ffff57b2b00, receiver=0x219bca0, e=0x22fea60) at kernel/qapplication.cpp:4423
#44 0x00007f218bd5aa86 in KApplication::notify (this=0x7ffff57b2b00, receiver=0x219bca0, event=0x22fea60) at /usr/src/debug/kdelibs-4.9.95/kdeui/kernel/kapplication.cpp:311
#45 0x00007f218afb8bfe in QCoreApplication::notifyInternal (this=0x7ffff57b2b00, receiver=receiver@entry=0x219bca0, event=event@entry=0x22fea60) at kernel/qcoreapplication.cpp:946
#46 0x00007f218afbc561 in sendEvent (event=0x22fea60, receiver=0x219bca0) at kernel/qcoreapplication.h:231
#47 QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, event_type=0, data=0x21172b0) at kernel/qcoreapplication.cpp:1570
#48 0x00007f218afe6f83 in sendPostedEvents () at kernel/qcoreapplication.h:236
#49 postEventSourceDispatch (s=0x21a6700) at kernel/qeventdispatcher_glib.cpp:279
#50 0x00007f21866e23b5 in g_main_context_dispatch () from /usr/lib64/libglib-2.0.so.0
#51 0x00007f21866e26e8 in ?? () from /usr/lib64/libglib-2.0.so.0
#52 0x00007f21866e27a4 in g_main_context_iteration () from /usr/lib64/libglib-2.0.so.0
#53 0x00007f218afe7116 in QEventDispatcherGlib::processEvents (this=0x211d790, flags=...) at kernel/qeventdispatcher_glib.cpp:424
#54 0x00007f218a1e6bee in QGuiEventDispatcherGlib::processEvents (this=<optimized out>, flags=...) at kernel/qguieventdispatcher_glib.cpp:204
#55 0x00007f218afb794f in QEventLoop::processEvents (this=this@entry=0x7ffff57b2880, flags=...) at kernel/qeventloop.cpp:149
#56 0x00007f218afb7bd8 in QEventLoop::exec (this=0x7ffff57b2880, flags=...) at kernel/qeventloop.cpp:204
#57 0x00007f218afbc878 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1218
#58 0x00007f21794f2a30 in kdemain (argc=1, argv=0x2186400) at /usr/src/debug/kdelibs-4.9.95/kded/kded.cpp:924
#59 0x0000000000408856 in launch (argc=argc@entry=1, _name=_name@entry=0x40b237 "kded4", args=args@entry=0x0, cwd=cwd@entry=0x0, envc=envc@entry=0, envs=<optimized out>, envs@entry=0x0, reset_env=reset_env@entry=false, tty=tty@entry=0x0, avoid_loops=avoid_loops@entry=false, startup_id_str=startup_id_str@entry=0x40b0c6 "0") at /usr/src/debug/kdelibs-4.9.95/kinit/kinit.cpp:726
#60 0x0000000000405f99 in main (argc=4, argv=<optimized out>, envp=0x7ffff57b34f0) at /usr/src/debug/kdelibs-4.9.95/kinit/kinit.cpp:1841
----------------------------------


Reproducible: Always

Steps to Reproduce:
1. compile and install recent git snapshot of libkscreen
2. compile and install recent git snapshot of kscreen
3. execute "qdbus org.kde.kded /kded org.kde.kded.unloadModule randrmonitor"
4. execute "qdbus org.kde.kded /kded org.kde.kded.setModuleAutoloading randrmonitor false"
5.  execute "qdbus org.kde.kded /kded org.kde.kded.loadModule kscreen"
6. restart KDE
Actual Results:  
kded crashes

Expected Results:  
kded does not crash

Maybe it is relevant that I have a dual graphics adapter setup:
- integrated Intel Arrandale chip with i915 driver
- Discrete AMD MobilityRadeon 5xxx with radeon driver

Nevertheless which adapter is enabled and which is disabled, kded crashes upon KDE startup