QmlDesigner: Crash fix

If the item did not have an id Qt Quick Designer crashed.
While we do ensure the item does get an id, we used the empty id
when refactoring later.
Now we use the generated id.

Change-Id: I71b9731270dc91537c17f6cb4fed3403d1001137
Reviewed-by: Tim Jenssen <tim.jenssen@theqtcompany.com>

src/plugins/qmldesigner/components/componentcore/modelnodeoperations.cpp

@@ -639,12 +639,9 @@ static QStringList getSortedSignalNameList(const ModelNode &modelNode)
 
 void gotoImplementation(const SelectionContext &selectionState)
 {
-    QString itemId;
     ModelNode modelNode;
-    if (selectionState.singleNodeIsSelected()) {
-        itemId = selectionState.selectedModelNodes().first().id();
+    if (selectionState.singleNodeIsSelected())
         modelNode = selectionState.selectedModelNodes().first();
-    }
 
     bool isModelNodeRoot = true;
 
@@ -670,6 +667,8 @@ void gotoImplementation(const SelectionContext &selectionState)
         }
     }
 
+    QString itemId = modelNode.id();
+
     const QString fileName = QmlDesignerPlugin::instance()->documentManager().currentDesignDocument()->fileName().toString();
     const QString typeName = QmlDesignerPlugin::instance()->documentManager().currentDesignDocument()->fileName().toFileInfo().baseName();