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.cpp

@@ -157,6 +157,13 @@ void QuickToolBar::apply(TextEditor::BaseTextEditorEditable *editor, Document::P
             end = objectBinding->lastSourceLocation().end();
         }
 
+        if (lookupContext.isNull()) {
+            if (name != m_oldType)
+                m_prototypes.clear();
+        }
+
+        m_oldType = name;
+
         m_prototypes.append(name);
 
         int line1;