### 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_MAIN_THREAD_GUARD;
	if (texture_mipmap_bias == p_texture_mipmap_bias) {
		return;
	}
	texture_mipmap_bias = p_texture_mipmap_bias;
	RS::get_singleton()->viewport_set_texture_mipmap_bias(viewport, p_texture_mipmap_bias);
}
float Viewport::get_texture_mipmap_bias() const {
	ERR_READ_THREAD_GUARD_V(0);
	return texture_mipmap_bias;
}
#endif 
void Viewport::_propagate_world_2d_changed(Node *p_node) {
	if (p_node != this) {
		if (Object::cast_to<CanvasItem>(p_node)) {
			p_node->notification(CanvasItem::NOTIFICATION_WORLD_2D_CHANGED);
		} else {
			Viewport *v = Object::cast_to<Viewport>(p_node);
			if (v) {
				if (v->world_2d.is_valid()) {
					return;
				}
			}
		}
	}
	for (int i = 0; i < p_node->get_child_count(); ++i) {
		_propagate_world_2d_changed(p_node->get_child(i));
	}
}
void Viewport::_bind_methods() {