backtrace file qgis with plugins disabled

$ gdb /usr/bin/qgis.bin core
GNU gdb (Ubuntu 7.7-0ubuntu3.1) 7.7
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Reading symbols from /usr/bin/qgis.bin...(no debugging symbols found)...done.
[New LWP 15409]
[New LWP 15410]
[New LWP 15412]
[New LWP 15418]
[New LWP 15424]
[New LWP 15429]
[New LWP 15425]
[New LWP 15426]
[New LWP 15436]
[New LWP 15411]
[New LWP 15432]
[New LWP 15413]
[New LWP 15431]
[New LWP 15430]
[New LWP 15427]
[New LWP 15423]
[New LWP 15428]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Core was generated by `/usr/bin/qgis.bin --noplugins'.
Program terminated with signal SIGABRT, Aborted.
#0  0x00007fe20f705bb9 in raise () from /lib/x86_64-linux-gnu/libc.so.6
(gdb) bt
#0  0x00007fe20f705bb9 in raise () from /lib/x86_64-linux-gnu/libc.so.6
#1  0x00007fe20f708fc8 in abort () from /lib/x86_64-linux-gnu/libc.so.6
#2  0x000000000050128c in qgisCrash(int) ()
#3  <signal handler called>
#4  0x00007fe2139ff081 in QgsLayerTreeLayer::layerName() const () from /usr/lib/libqgis_core.so.2.6.0
#5  0x00007fe2139ff3f3 in QgsLayerTreeLayer::writeXML(QDomElement&) () from /usr/lib/libqgis_core.so.2.6.0
#6  0x00007fe2139fc6c6 in QgsLayerTreeGroup::writeXML(QDomElement&) () from /usr/lib/libqgis_core.so.2.6.0
#7  0x00007fe213c75c37 in QgsComposerLegend::writeXML(QDomElement&, QDomDocument&) const () from /usr/lib/libqgis_core.so.2.6.0
#8  0x00007fe213c89bc0 in QgsComposition::writeXML(QDomElement&, QDomDocument&) () from /usr/lib/libqgis_core.so.2.6.0
#9  0x000000000074d06b in QgsComposer::writeXML(QDomNode&, QDomDocument&) ()
#10 0x000000000074d290 in QgsComposer::writeXML(QDomDocument&) ()
#11 0x000000000084059e in ?? ()
#12 0x00007fe2128b587a in QMetaObject::activate(QObject*, QMetaObject const*, int, void**) ()
   from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#13 0x00007fe213d11245 in QgsProject::writeProject(QDomDocument&) () from /usr/lib/libqgis_core.so.2.6.0
#14 0x00007fe213b75b6c in QgsProject::write() () from /usr/lib/libqgis_core.so.2.6.0
#15 0x000000000052e79b in QgisApp::fileSave() ()
#16 0x0000000000832e4d in ?? ()
#17 0x00007fe2128b587a in QMetaObject::activate(QObject*, QMetaObject const*, int, void**) ()
   from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#18 0x00007fe211c34a62 in QAction::triggered(bool) () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#19 0x00007fe211c36433 in QAction::activate(QAction::ActionEvent) () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#20 0x00007fe211fedb02 in ?? () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
---Type <return> to continue, or q <return> to quit---
#21 0x00007fe211fedc2c in QAbstractButton::mouseReleaseEvent(QMouseEvent*) () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#22 0x00007fe2120a4a4a in QToolButton::mouseReleaseEvent(QMouseEvent*) () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#23 0x00007fe211c8a50a in QWidget::event(QEvent*) () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#24 0x00007fe211c3ae2c in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#25 0x00007fe211c415dd in QApplication::notify(QObject*, QEvent*) () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#26 0x00007fe213a1976b in QgsApplication::notify(QObject*, QEvent*) () from /usr/lib/libqgis_core.so.2.6.0
#27 0x00007fe2128a14dd in QCoreApplication::notifyInternal(QObject*, QEvent*) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#28 0x00007fe211c40d93 in QApplicationPrivate::sendMouseEvent(QWidget*, QMouseEvent*, QWidget*, QWidget*, QWidget**, QPointer<QWidget>&, bool) () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#29 0x00007fe211cb59cb in ?? () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#30 0x00007fe211cb5269 in QApplication::x11ProcessEvent(_XEvent*) () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#31 0x00007fe211cdcb02 in ?? () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#32 0x00007fe20d55ee04 in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#33 0x00007fe20d55f048 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#34 0x00007fe20d55f0ec in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#35 0x00007fe2128ce7a1 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) ()
   from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#36 0x00007fe211cdcbb6 in ?? () from /usr/lib/x86_64-linux-gnu/libQtGui.so.4
#37 0x00007fe2128a00af in QEventLoop::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) ()
   from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#38 0x00007fe2128a03a5 in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#39 0x00007fe2128a5b79 in QCoreApplication::exec() () from /usr/lib/x86_64-linux-gnu/libQtCore.so.4
#40 0x00000000004fbd90 in main ()
(gdb) quit