### 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(VRS_DISABLED);
	return vrs_mode;
}
void Viewport::set_vrs_texture(Ref<Texture2D> p_texture) {
	ERR_MAIN_THREAD_GUARD;
	vrs_texture = p_texture;
	
	RID tex = p_texture.is_valid() ? p_texture->get_rid() : RID();
	RS::get_singleton()->viewport_set_vrs_texture(viewport, tex);
}
Ref<Texture2D> Viewport::get_vrs_texture() const {
	ERR_READ_THREAD_GUARD_V(Ref<Texture2D>());
	return vrs_texture;
}
DisplayServer::WindowID Viewport::get_window_id() const {
	ERR_READ_THREAD_GUARD_V(DisplayServer::INVALID_WINDOW_ID);
	return DisplayServer::MAIN_WINDOW_ID;
}
Viewport *Viewport::get_parent_viewport() const {
	ERR_READ_THREAD_GUARD_V(nullptr);
	ERR_FAIL_COND_V(!is_inside_tree(), nullptr);
	if (!get_parent()) {
		return nullptr; 
	}
	return get_parent()->get_viewport();
}
void Viewport::set_embedding_subwindows(bool p_embed) {