I dragged a new network information widget to the task bar and KDE crashed when I let go the mouse button.

Reproducible: Didn't try

Steps to Reproduce:
1. Right click on task bar, select "Panel Options > add widgets.
2. Select widget and drag to task bar, then let go mouse button.
3.

Actual Results:  
Black screen, with KDE bug report form.

Expected Results:  
Shiny new widget in task bar.

Application: plasma-desktop (4.11.11)
KDE Platform Version: 4.13.3
Qt Version: 4.8.6
Operating System: Linux 3.13.0-66-generic x86_64
Distribution: Ubuntu 14.04.3 LTS

-- Information about the crash:
- What I was doing when the application crashed:
I selected a network information widget and dragged it to the task bar, as soon as I let go the mouse button KDE crashed.

-- Backtrace:
Application: Plasma Desktop Shell (plasma-desktop), signal: Segmentation fault
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[Current thread is 1 (Thread 0x7f7c690a77c0 (LWP 3689))]

Thread 4 (Thread 0x7f7c3e571700 (LWP 3694)):
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1  0x00007f7c61d54ffb in ?? () from /usr/lib/x86_64-linux-gnu/libQtScript.so.4
#2  0x00007f7c61d55039 in ?? () from /usr/lib/x86_64-linux-gnu/libQtScript.so.4
#3  0x00007f7c5c600182 in start_thread (arg=0x7f7c3e571700) at pthread_create.c:312
#4  0x00007f7c689a147d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

Thread 3 (Thread 0x7f7bb8609700 (LWP 3697)):
#0  __pthread_mutex_unlock_usercnt (decr=1, mutex=0x7f7bb0000a60) at pthread_mutex_unlock.c:51
#1  __GI___pthread_mutex_unlock (mutex=0x7f7bb0000a60) at pthread_mutex_unlock.c:310
#2  0x00007f7c5bf309b1 in g_mutex_unlock () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#3  0x00007f7c5beeefd9 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#4  0x00007f7c5beef0ec in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#5  0x00007f7c6556a7be in QEventDispatcherGlib::processEvents (this=0x7f7bb00008c0, flags=...) at kernel/qeventdispatcher_glib.cpp:436
#6  0x00007f7c6553c0af in QEventLoop::processEvents (this=this@entry=0x7f7bb8608de0, flags=...) at kernel/qeventloop.cpp:149
#7  0x00007f7c6553c3a5 in QEventLoop::exec (this=this@entry=0x7f7bb8608de0, flags=...) at kernel/qeventloop.cpp:204
#8  0x00007f7c65438c5f in QThread::exec (this=this@entry=0x31e56b0) at thread/qthread.cpp:537
#9  0x00007f7c6551d823 in QInotifyFileSystemWatcherEngine::run (this=0x31e56b0) at io/qfilesystemwatcher_inotify.cpp:265
#10 0x00007f7c6543b32f in QThreadPrivate::start (arg=0x31e56b0) at thread/qthread_unix.cpp:349
#11 0x00007f7c5c600182 in start_thread (arg=0x7f7bb8609700) at pthread_create.c:312
#12 0x00007f7c689a147d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

Thread 2 (Thread 0x7f7bb63cb700 (LWP 3699)):
#0  0x00007f7c5bf309a0 in g_mutex_unlock () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#1  0x00007f7c5beee8f9 in g_main_context_query () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#2  0x00007f7c5beeef52 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#3  0x00007f7c5beef0ec in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#4  0x00007f7c6556a7be in QEventDispatcherGlib::processEvents (this=0x7f7ba80008c0, flags=...) at kernel/qeventdispatcher_glib.cpp:436
#5  0x00007f7c6553c0af in QEventLoop::processEvents (this=this@entry=0x7f7bb63cade0, flags=...) at kernel/qeventloop.cpp:149
#6  0x00007f7c6553c3a5 in QEventLoop::exec (this=this@entry=0x7f7bb63cade0, flags=...) at kernel/qeventloop.cpp:204
#7  0x00007f7c65438c5f in QThread::exec (this=this@entry=0x326f600) at thread/qthread.cpp:537
#8  0x00007f7c6551d823 in QInotifyFileSystemWatcherEngine::run (this=0x326f600) at io/qfilesystemwatcher_inotify.cpp:265
#9  0x00007f7c6543b32f in QThreadPrivate::start (arg=0x326f600) at thread/qthread_unix.cpp:349
#10 0x00007f7c5c600182 in start_thread (arg=0x7f7bb63cb700) at pthread_create.c:312
#11 0x00007f7c689a147d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

Thread 1 (Thread 0x7f7c690a77c0 (LWP 3689)):
[KCrash Handler]
#6  QMutex::lock (this=this@entry=0x8d) at thread/qmutex.cpp:150
#7  0x00007f7c65541139 in QCoreApplication::postEvent (receiver=receiver@entry=0x3baf610, event=0x6a1b830, priority=priority@entry=0) at kernel/qcoreapplication.cpp:1358
#8  0x00007f7c65541427 in QCoreApplication::postEvent (receiver=receiver@entry=0x3baf610, event=<optimized out>) at kernel/qcoreapplication.cpp:1311
#9  0x00007f7c6554f094 in QObject::deleteLater (this=this@entry=0x3baf610) at kernel/qobject.cpp:2087
#10 0x00007f7c6495ebaf in QX11Data::xdndHandleFinished (this=<optimized out>, xe=0x7ffe7e5e0590, passive=<optimized out>) at kernel/qdnd_x11.cpp:1256
#11 0x00007f7c64940fe3 in QApplication::x11ClientMessage (this=<optimized out>, w=0x80ec040, event=<optimized out>, passive_only=<optimized out>) at kernel/qapplication_x11.cpp:3259
#12 0x00007f7c64950892 in QApplication::x11ProcessEvent (this=0x242fcc0, event=event@entry=0x7ffe7e5e0590) at kernel/qapplication_x11.cpp:3888
#13 0x00007f7c64978b32 in x11EventSourceDispatch (s=0x244d630, callback=0x0, user_data=0x0) at kernel/qguieventdispatcher_glib.cpp:146
#14 0x00007f7c5beeee04 in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#15 0x00007f7c5beef048 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#16 0x00007f7c5beef0ec in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#17 0x00007f7c6556a7a1 in QEventDispatcherGlib::processEvents (this=0x23c6af0, flags=...) at kernel/qeventdispatcher_glib.cpp:434
#18 0x00007f7c64978be6 in QGuiEventDispatcherGlib::processEvents (this=<optimized out>, flags=...) at kernel/qguieventdispatcher_glib.cpp:204
#19 0x00007f7c6553c0af in QEventLoop::processEvents (this=this@entry=0x7ffe7e5e0960, flags=...) at kernel/qeventloop.cpp:149
#20 0x00007f7c6553c3a5 in QEventLoop::exec (this=this@entry=0x7ffe7e5e0960, flags=...) at kernel/qeventloop.cpp:204
#21 0x00007f7c65541b79 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1225
#22 0x00007f7c68ca867c in kdemain () from /usr/lib/kde4/libkdeinit/libkdeinit4_plasma-desktop.so
#23 0x00007f7c688c8ec5 in __libc_start_main (main=0x4006e0, argc=1, argv=0x7ffe7e5e0bb8, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7ffe7e5e0ba8) at libc-start.c:287
#24 0x000000000040070e in _start ()

Possible duplicates by query: bug 225190, bug 225111, bug 224804, bug 224631, bug 224505.

Report to https://bugs.kde.org/