QuickToolBar: critical bugfix

The protype chain is cached in m_prototypes,
but the type might have changed.
We have to check for this case.

Reviewed-by: Lasse Holmstedt

src/plugins/qmljseditor/quicktoolbar.h

@@ -53,6 +53,7 @@ private:
     bool m_blockWriting;
     QStringList m_propertyOrder;
     QStringList m_prototypes;
+    QString m_oldType;
 };
 
 } //QmlDesigner