Prevent to make UndoRedo for duplicate if no selected node

(cherry picked from commit d82928eb494d3d0856eac85e82b9cd835a368f96)

tools/editor/scene_tree_dock.cpp

@@ -460,6 +460,8 @@ void SceneTreeDock::_tool_selected(int p_tool, bool p_confirm_override) {
 				break;
 
 			List<Node*> selection = editor_selection->get_selected_node_list();
+			if (selection.size()==0)
+				break;
 
 			List<Node*> reselect;