Crash on unload and reload language

[Aleix]

Hi list,
I've noticed that if I load a language, unload and load it again, then
KDevelop4 crashes.

Crash recipe:
- Open a cmake project
- Open a CMakeLists.txt file
- Close the project
- Open another cmake project
- Open a CMakeLists.txt file
- **crash**

My theory is that it is crashing because it is trying to use the old
languageSupport for the new file, I don't really know this code, so
I'm a bit scared of changing things there...

Cheers!
Aleix

#0  0xb61b71f0 in KDevelop::DUChainUtils::standardContextForUrl
(url=@0xbfe6b014) at
/home/kde-devel/kdevplatform/language/duchain/duchainutils.cpp:218
#1  0xb61831cd in KDevelop::DUChain::documentLoadedPrepare
(this=0x81da328, doc=0x875b580) at
/home/kde-devel/kdevplatform/language/duchain/duchain.cpp:399
#2  0xb618484a in KDevelop::DUChain::qt_metacall (this=0x81da328,
_c=QMetaObject::InvokeMetaMethod, _id=2, _a=0xbfe6b14c)
    at /home/kde-devel/build-kdevplatform/language/duchain.moc:72
#3  0xb73ca423 in QMetaObject::activate (sender=0x817ad48,
from_signal_index=10, to_signal_index=10, argv=0xbfe6b14c) at
kernel/qobject.cpp:2998
#4  0xb73ca8a5 in QMetaObject::activate (sender=0x817ad48,
m=0xb615f5dc, local_signal_index=6, argv=0xbfe6b14c) at
kernel/qobject.cpp:3071
#5  0xb6159ce8 in KDevelop::IDocumentController::documentLoadedPrepare
(this=0x817ad48, _t1=0x875b580)
    at /home/kde-devel/build-kdevplatform/interfaces/idocumentcontroller.moc:186
#6  0xb7cf4f58 in KDevelop::DocumentController::openDocument
(this=0x817ad48, inputUrl=@0x84cc464, cursor=@0xbfe6b30c,
activationParams=@0xbfe6b308)
    at /home/kde-devel/kdevplatform/shell/documentcontroller.cpp:368
#7  0xb279d0eb in ProjectManagerPrivate::openUrl (this=0x867c5e8,
url=@0x84cc464)
    at /home/kde-devel/kdevplatform/plugins/projectmanagerview/projectmanagerview.cpp:87
#8  0xb279baa0 in ProjectManagerView::qt_metacall (this=0x86a1198,
_c=QMetaObject::InvokeMetaMethod, _id=1, _a=0xbfe6b42c)
    at /home/kde-devel/build-kdevplatform/plugins/projectmanagerview/projectmanagerview.moc:72
#9  0xb73ca423 in QMetaObject::activate (sender=0x86a11e8,
from_signal_index=91, to_signal_index=91, argv=0xbfe6b42c) at
kernel/qobject.cpp:2998
#10 0xb73ca8a5 in QMetaObject::activate (sender=0x86a11e8,
m=0xb27a54a8, local_signal_index=0, argv=0xbfe6b42c) at
kernel/qobject.cpp:3071
#11 0xb279d62e in ProjectTreeView::activateUrl (this=0x86a11e8, _t1=@0x84cc464)
    at /home/kde-devel/build-kdevplatform/plugins/projectmanagerview/projecttreeview.moc:92
#12 0xb279e92e in ProjectTreeView::slotActivated (this=0x86a11e8,
index=@0x8650be0)
    at /home/kde-devel/kdevplatform/plugins/projectmanagerview/projecttreeview.cpp:170
#13 0xb279e9ea in ProjectTreeView::qt_metacall (this=0x86a11e8,
_c=QMetaObject::InvokeMetaMethod, _id=2, _a=0xbfe6b57c)
    at /home/kde-devel/build-kdevplatform/plugins/projectmanagerview/projecttreeview.moc:78
#14 0xb73ca423 in QMetaObject::activate (sender=0x86a11e8,
from_signal_index=33, to_signal_index=33, argv=0xbfe6b57c) at
kernel/qobject.cpp:2998
#15 0xb73ca8a5 in QMetaObject::activate (sender=0x86a11e8,
m=0xb6f1c084, local_signal_index=2, argv=0xbfe6b57c) at
kernel/qobject.cpp:3071
#16 0xb6d1c3c0 in QAbstractItemView::doubleClicked (this=0x86a11e8,
_t1=@0x8650be0) at .moc/debug-shared/moc_qabstractitemview.cpp:323
#17 0xb6d629c5 in QTreeView::mouseDoubleClickEvent (this=0x86a11e8,
event=0xbfe6c094) at itemviews/qtreeview.cpp:1781
#18 0xb687ece5 in QWidget::event (this=0x86a11e8, event=0xbfe6c094) at
kernel/qwidget.cpp:6924