QmlDesigner: Fix node instance view notifications

Fix node instance view notifications and settings in the model.
Now the old node instance view is detached and the new one is attached.
The test runs again. Also fixes a notification.

src/plugins/qmldesigner/designercore/model/model.cpp

@@ -417,7 +417,7 @@ void ModelPrivate::notifyCustomNotification(const AbstractView *senderView, cons
     }
 
     if (nodeInstanceView()) {
-        rewriterView()->customNotification(senderView, identifier, toModelNodeList(internalList, nodeInstanceView()), data);
+        nodeInstanceView()->customNotification(senderView, identifier, toModelNodeList(internalList, nodeInstanceView()), data);
     }
 
     if (resetModel) {
@@ -1192,14 +1192,14 @@ void ModelPrivate::setNodeInstanceView(NodeInstanceView *nodeInstanceView)
     if (nodeInstanceView == m_nodeInstanceView.data())
         return;
 
-    Q_ASSERT(!(nodeInstanceView && m_nodeInstanceView));
+    if (m_nodeInstanceView)
+        m_nodeInstanceView->modelAboutToBeDetached(m_q);
 
     m_nodeInstanceView = nodeInstanceView;
 
     if (nodeInstanceView)
         nodeInstanceView->modelAttached(m_q);
-    else if (m_nodeInstanceView)
-        m_nodeInstanceView->modelAttached(m_q);
+
 }
 
 NodeInstanceView *ModelPrivate::nodeInstanceView() const