### Godot version

Master (4.2)

### System information

Windows 11 - Vulkan - Nvidia RTX 4070 - intel i5 13600KF

### Issue description

As you can see in the video when you try to add multiple scenes in to the 3D viewport (only with multiple scenes) the editor throws this error.

```
ERROR: Can't add child '@Node3D@18837' to '@SubViewport@9274', already has a parent '@SubViewport@9274'.
   at: (scene\main\node.cpp:1411)
```


Video: https://youtu.be/BVcCIigQJDw

This happens in the latest master (pulled on 2.11.2023).

### Steps to reproduce

Drag couple of the 3d mesh scenes into the 3D viewport and then select multiple scenes and drag them over and observer the error.

### Minimal reproduction project

[TestSceneDragAndDrop.zip](https://github.com/godotengine/godot/files/13253741/TestSceneDragAndDrop.zip)

_refresh_menu_icons();
	if (selected && editor_selection->get_selected_node_list().size() != 1) {
		Vector<Ref<Node3DGizmo>> gizmos = selected->get_gizmos();
		for (int i = 0; i < gizmos.size(); i++) {
			Ref<EditorNode3DGizmo> seg = gizmos[i];
			if (!seg.is_valid()) {
				continue;
			}
			seg->set_selected(false);
		}
		Node3DEditorSelectedItem *se = editor_selection->get_node_editor_data<Node3DEditorSelectedItem>(selected);
		if (se) {
			se->gizmo.unref();
			se->subgizmos.clear();
		}
		selected->update_gizmos();
		selected = nullptr;
	}
	update_transform_gizmo();
}
void Node3DEditor::_refresh_menu_icons() {