This affects git master as well as the latest release.

STEPS TO REPRODUCE
1. Open a file
2. Play it
3. Click "Play Media" to go back to the Playlist view
4. Double-click on the item for the currently playing piece of media

OBSERVED RESULT
100% reproducible crash:

#0  0x00007ffff5aed17f in QThreadStorageData::get() const (this=this@entry=0x0)
    at thread/qthreadstorage.cpp:122
#1  0x00007ffff5acfa77 in QThreadStorage<QUnifiedTimer*>::hasLocalData() const (this=0x0)
    at ../../include/QtCore/../../src/corelib/thread/qthreadstorage.h:141
#2  QUnifiedTimer::instance(bool) (create=<optimized out>) at animation/qabstractanimation.cpp:234
#3  0x00007ffff5acfc12 in QAnimationDriver::advanceAnimation(long long)
    (this=<optimized out>, timeStep=-1) at animation/qabstractanimation.cpp:820
#4  0x00007ffff5cd2ad5 in QObject::event(QEvent*) (this=0x59f008, e=0x7fffffffd220)
    at kernel/qobject.cpp:1369
#5  0x00007ffff69aed02 in QApplicationPrivate::notify_helper(QObject*, QEvent*)
    (this=<optimized out>, receiver=0x59f008, e=0x7fffffffd220) at kernel/qapplication.cpp:3637
#6  0x00007ffff5ca81c8 in QCoreApplication::notifyInternal2(QObject*, QEvent*)
    (receiver=0x59f008, event=0x7fffffffd220) at kernel/qcoreapplication.cpp:1064
#7  0x00007ffff5cf83b1 in QTimerInfoList::activateTimers() (this=0x553af0)
    at kernel/qtimerinfo_unix.cpp:643
#8  0x00007ffff5cf8c8c in timerSourceDispatch(GSource*, GSourceFunc, gpointer)
    (source=<optimized out>) at kernel/qeventdispatcher_glib.cpp:183
#9  0x00007ffff4526faf in g_main_dispatch (context=0x7fffdc005010) at ../glib/gmain.c:3417
#10 g_main_context_dispatch (context=0x7fffdc005010) at ../glib/gmain.c:4135
#11 0x00007ffff457c2c8 in g_main_context_iterate.constprop.0
    (context=context@entry=0x7fffdc005010, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at ../glib/gmain.c:4211
#12 0x00007ffff4524940 in g_main_context_iteration (context=0x7fffdc005010, may_block=1)
    at ../glib/gmain.c:4276
#13 0x00007ffff5cf902a in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>)
    (this=0x54d010, flags=...) at kernel/qeventdispatcher_glib.cpp:423
#14 0x00007ffff5ca6c1a in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>)
    (this=this@entry=0x7fffffffd4c0, flags=..., flags@entry=...)
    at ../../include/QtCore/../../src/corelib/global/qflags.h:69
#15 0x00007ffff5caece2 in QCoreApplication::exec() ()
    at ../../include/QtCore/../../src/corelib/global/qflags.h:121
#16 0x00007ffff615fbe0 in QGuiApplication::exec() () at kernel/qguiapplication.cpp:1863
#17 0x00007ffff69aec79 in QApplication::exec() () at kernel/qapplication.cpp:2829
#18 0x000000000041c0ff in main(int, char**) (argc=<optimized out>, argv=<optimized out>)
    at /home/nate/kde/src/dragon/src/app/main.cpp:80

log output says:

QObject::startTimer: Timers cannot be started from another thread
QObject::killTimer: Timers cannot be stopped from another thread
QObject::startTimer: Timers cannot be started from another thread
QObject::startTimer: Timers can only be used with threads started with QThread