Dragging a Fret diagram to a Fret diagram frame gives segfault

GIT commit: b9984ff

By playing around, I've had another crash. I don't know if this is a proper way of adding fret diagrams, but at least it shouldn't crash if you do it. It's easy to reproduce:

1. create a new document with one guitar pitch staff
2. click on Frames and drag a Fret diagram frame to the sheet
3. click on Symbols and drag a Fret diagram to the frame created in previous step.

This will make MuseScore crash. I'm using Ubuntu 12.04. Here follows a backtrace:

Program received signal SIGSEGV, Segmentation fault.
0x00000000006a4e9b in QListData::size (this=0x5ed2f10) at /usr/include/qt4/QtCore/qlist.h:98
98 inline int size() const { return d->end - d->begin; }
(gdb) bt
#0 0x00000000006a4e9b in QListData::size (this=0x5ed2f10) at /usr/include/qt4/QtCore/qlist.h:98
#1 0x00000000006a99ca in QList::size (this=0x5ed2f10) at /usr/include/qt4/QtCore/qlist.h:137
#2 0x0000000000b12d26 in System::staffY (this=0x5ed2e40, staffIdx=0) at /home/johan/Projects/MuseScore/libmscore/system.cpp:982
#3 0x0000000000a51769 in FretDiagram::pagePos (this=0x1842830) at /home/johan/Projects/MuseScore/libmscore/fret.cpp:102
#4 0x00000000006a679f in Element::abbox (this=0x1842830) at /home/johan/Projects/MuseScore/libmscore/element.h:349
#5 0x0000000000ad0f4c in Score::select (this=0x5e9ddc0, e=0x1842830, type=SELECT_SINGLE, staffIdx=0)
at /home/johan/Projects/MuseScore/libmscore/score.cpp:2755
#6 0x00000000009b4c0c in ScoreView::dropEvent (this=0x5ed9620, event=0x7fffffffb0a0)
at /home/johan/Projects/MuseScore/mscore/dragdrop.cpp:453
#7 0x00007ffff4435491 in QWidget::event(QEvent*) () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#8 0x000000000069e92d in ScoreView::event (this=0x5ed9620, event=0x7fffffffb0a0) at /home/johan/Projects/MuseScore/mscore/scoreview.cpp:3728
#9 0x00007ffff43e4894 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#10 0x00007ffff43e9c5f in QApplication::notify(QObject*, QEvent*) () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#11 0x00007ffff3932e9c in QCoreApplication::notifyInternal(QObject*, QEvent*) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#12 0x00007ffff446f163 in ?? () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#13 0x00007ffff44706f3 in ?? () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#14 0x00007ffff4473488 in ?? () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#15 0x00007ffff3932f6c in QCoreApplicationPrivate::sendThroughApplicationEventFilters(QObject*, QEvent*) ()
from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#16 0x00007ffff43e4806 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#17 0x00007ffff43ea0bf in QApplication::notify(QObject*, QEvent*) () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#18 0x00007ffff3932e9c in QCoreApplication::notifyInternal(QObject*, QEvent*) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#19 0x00007ffff43e5862 in QApplicationPrivate::sendMouseEvent(QWidget*, QMouseEvent*, QWidget*, QWidget*, QWidget**, QPointer&, bool)
() from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#20 0x00007ffff4464bf5 in ?? () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#21 0x00007ffff4463bae in QApplication::x11ProcessEvent(_XEvent*) () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#22 0x00007ffff448d0d2 in ?? () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#23 0x00007fffefaa0d53 in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#24 0x00007fffefaa10a0 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#25 0x00007fffefaa1164 in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#26 0x00007ffff39623bf in QEventDispatcherGlib::processEvents(QFlags) ()
from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#27 0x00007ffff448cd5e in ?? () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#28 0x00007ffff3931c82 in QEventLoop::processEvents(QFlags) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#29 0x00007ffff3931ed7 in QEventLoop::exec(QFlags) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#30 0x00007ffff4473183 in ?? () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#31 0x00007ffff43f6613 in QDrag::start(QFlags) () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#32 0x00000000007c6433 in Palette::mouseMoveEvent (this=0x5670b60, ev=0x7fffffffcfd0) at /home/johan/Projects/MuseScore/mscore/palette.cpp:357
---Type to continue, or q to quit---
#33 0x00007ffff4435178 in QWidget::event(QEvent*) () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#34 0x00000000007c7c19 in Palette::event (this=0x5670b60, ev=0x7fffffffcfd0) at /home/johan/Projects/MuseScore/mscore/palette.cpp:629
#35 0x00007ffff43e4894 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#36 0x00007ffff43ea0bf in QApplication::notify(QObject*, QEvent*) () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#37 0x00007ffff3932e9c in QCoreApplication::notifyInternal(QObject*, QEvent*) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#38 0x00007ffff43e5862 in QApplicationPrivate::sendMouseEvent(QWidget*, QMouseEvent*, QWidget*, QWidget*, QWidget**, QPointer&, bool)
() from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#39 0x00007ffff4464bf5 in ?? () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#40 0x00007ffff4463bae in QApplication::x11ProcessEvent(_XEvent*) () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#41 0x00007ffff448d0d2 in ?? () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#42 0x00007fffefaa0d53 in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#43 0x00007fffefaa10a0 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#44 0x00007fffefaa1164 in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#45 0x00007ffff39623bf in QEventDispatcherGlib::processEvents(QFlags) ()
from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#46 0x00007ffff448cd5e in ?? () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#47 0x00007ffff3931c82 in QEventLoop::processEvents(QFlags) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#48 0x00007ffff3931ed7 in QEventLoop::exec(QFlags) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#49 0x00007ffff3936f67 in QCoreApplication::exec() () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#50 0x000000000079fc94 in main (argc=1, av=0x7fffffffe238) at /home/johan/Projects/MuseScore/mscore/musescore.cpp:2475
(gdb)