Step to reproduce:
1. Open/Create new console qt application
2. Open main.cpp(do not close it!!!)
3. Close project =>after few seconds => crash

Stacktrace:
0 QCleanlooksStyle::styleHint(QStyle::StyleHint, QStyleOption const*, QWidget const*, QStyleHintReturn*) const /usr/lib/x86_64-linux-gnu/libQtGui.so.4 0 0x7ffff742e291
1 ManhattanStyle::styleHint manhattanstyle.cpp 351 0x7fffee8916cc
2 QMenuBar::eventFilter(QObject*, QEvent*) /usr/lib/x86_64-linux-gnu/libQtGui.so.4 0 0x7ffff74e923e
3 QCoreApplicationPrivate::sendThroughObjectEventFilters(QObject*, QEvent*) /usr/lib/x86_64-linux-gnu/libQtCore.so.4 0 0x7ffff6820028
4 QApplicationPrivate::notify_helper(QObject*, QEvent*) /usr/lib/x86_64-linux-gnu/libQtGui.so.4 0 0x7ffff708e85f
5 QApplication::notify(QObject*, QEvent*) /usr/lib/x86_64-linux-gnu/libQtGui.so.4 0 0x7ffff7093713
6 QCoreApplication::notifyInternal(QObject*, QEvent*) /usr/lib/x86_64-linux-gnu/libQtCore.so.4 0 0x7ffff681fe9c
7 ?? /usr/lib/x86_64-linux-gnu/libQtGui.so.4 0 0x7ffff7087861
8 Utils::ProxyAction::update proxyaction.cpp 131 0x7fffee508669
9 Utils::ProxyAction::actionChanged proxyaction.cpp 109 0x7fffee5084a5
10 Utils::ProxyAction::qt_static_metacall moc_proxyaction.cpp 52 0x7fffee5184d7
11 QMetaObject::activate(QObject*, QMetaObject const*, int, void**) /usr/lib/x86_64-linux-gnu/libQtCore.so.4 0 0x7ffff6834281
12 ?? /usr/lib/x86_64-linux-gnu/libQtGui.so.4 0 0x7ffff7087905
13 Utils::ParameterAction::setParameter parameteraction.cpp 97 0x7fffee4d10ed
14 Qt4ProjectManager::Internal::Qt4ProjectManagerPlugin::updateContextActions qt4projectmanagerplugin.cpp 367 0x7fffce12bf59
15 Qt4ProjectManager::Internal::Qt4ProjectManagerPlugin::qt_static_metacall moc_qt4projectmanagerplugin.cpp 64 0x7fffce1ebb85
16 QMetaObject::activate(QObject*, QMetaObject const*, int, void**) /usr/lib/x86_64-linux-gnu/libQtCore.so.4 0 0x7ffff6834281
17 ProjectExplorer::ProjectExplorerPlugin::currentNodeChanged moc_projectexplorer.cpp 424 0x7fffd2b1db79
18 ProjectExplorer::ProjectExplorerPlugin::setCurrent projectexplorer.cpp 1820 0x7fffd29890c6
19 ProjectExplorer::ProjectExplorerPlugin::setCurrentFile projectexplorer.cpp 1422 0x7fffd2986a3b
20 ProjectExplorer::ProjectExplorerPlugin::qt_static_metacall moc_projectexplorer.cpp 299 0x7fffd2b1d5cc
... <More>