QmlDesigner.Navigator: Root node is not collapsable

src/plugins/qmldesigner/components/navigator/navigatorwidget.cpp

@@ -81,6 +81,7 @@ void NavigatorWidget::setTreeModel(QAbstractItemModel* model)
     m_treeView->setModel(model);
     m_treeView->header()->setResizeMode(0, QHeaderView::Stretch);
     m_treeView->header()->resizeSection(1,20);
+    m_treeView->setRootIsDecorated(false);
 #ifdef _LOCK_ITEMS_
     m_treeView->header()->resizeSection(2,20);
 #endif