QmlDesigner: crash fix

There can be holes in the prototype chain. This can lead to a type being
its own prototype.

Task-number: QTCREATORBUG-7300
Change-Id: I10c76decdf3d6490d468ad9dd1ea65f0cbacdfbb
Reviewed-by: Marco Bubke <marco.bubke@nokia.com>
Reviewed-by: Alessandro Portale <alessandro.portale@nokia.com>

src/plugins/qmldesigner/designercore/metainfo/nodemetainfo.cpp

@@ -269,6 +269,9 @@ QList<PropertyInfo> getObjectTypes(const ObjectValue *ov, const ContextPtr &cont
     if (!local) {
         const ObjectValue* prototype = ov->prototype(context);
 
+        if (prototype == ov)
+            return list;
+
         const CppComponentValue * qmlObjectValue = value_cast<CppComponentValue>(prototype);
 
         if (qmlObjectValue) {