### Godot version

v4.0 rc6

### System information

Windows 10

### Issue description

When using a ViewportTexture from a SubViewport on a TextureRect, it throws errors after running the scene once and then switching scenes in the editor.
![Pasted image 20230227212626](https://user-images.githubusercontent.com/44676282/221680047-984fa03e-33d1-4856-9a7f-1700b28423cf.png)


### Steps to reproduce

Run the canvas-scene once.
Switch to another scene in the editor.
Switch back to the canvas-scene

### Minimal reproduction project

[ViewportTextureError.zip](https://github.com/godotengine/godot/files/10844099/ViewportTextureError.zip)

ERR_READ_THREAD_GUARD_V(Ref<World2D>());
	if (world_2d.is_valid()) {
		return world_2d;
	} else if (parent) {
		return parent->find_world_2d();
	} else {
		return Ref<World2D>();
	}
}
void Viewport::_propagate_viewport_notification(Node *p_node, int p_what) {
	p_node->notification(p_what);
	for (int i = 0; i < p_node->get_child_count(); i++) {
		Node *c = p_node->get_child(i);
		if (Object::cast_to<Viewport>(c)) {
			continue;
		}
		_propagate_viewport_notification(c, p_what);
	}
}
Ref<World2D> Viewport::get_world_2d() const {
	ERR_READ_THREAD_GUARD_V(Ref<World2D>());
	return world_2d;
}
Camera2D *Viewport::get_camera_2d() const {