### 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)

if (preview_node->get_parent()) {
		for (int i = preview_node->get_child_count() - 1; i >= 0; i--) {
			Node *node = preview_node->get_child(i);
			node->queue_free();
			preview_node->remove_child(node);
		}
		EditorNode::get_singleton()->get_scene_root()->remove_child(preview_node);
	}
}
bool Node3DEditorViewport::_apply_preview_material(ObjectID p_target, const Point2 &p_point) const {