### 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(DEFAULT_CANVAS_ITEM_TEXTURE_FILTER_NEAREST);
	return default_canvas_item_texture_filter;
}
void Viewport::set_default_canvas_item_texture_repeat(DefaultCanvasItemTextureRepeat p_repeat) {
	ERR_MAIN_THREAD_GUARD;
	ERR_FAIL_INDEX(p_repeat, DEFAULT_CANVAS_ITEM_TEXTURE_REPEAT_MAX);
	if (default_canvas_item_texture_repeat == p_repeat) {
		return;
	}
	default_canvas_item_texture_repeat = p_repeat;
	switch (default_canvas_item_texture_repeat) {
		case DEFAULT_CANVAS_ITEM_TEXTURE_REPEAT_DISABLED:
			RS::get_singleton()->viewport_set_default_canvas_item_texture_repeat(viewport, RS::CANVAS_ITEM_TEXTURE_REPEAT_DISABLED);
			break;
		case DEFAULT_CANVAS_ITEM_TEXTURE_REPEAT_ENABLED:
			RS::get_singleton()->viewport_set_default_canvas_item_texture_repeat(viewport, RS::CANVAS_ITEM_TEXTURE_REPEAT_ENABLED);
			break;
		case DEFAULT_CANVAS_ITEM_TEXTURE_REPEAT_MIRROR:
			RS::get_singleton()->viewport_set_default_canvas_item_texture_repeat(viewport, RS::CANVAS_ITEM_TEXTURE_REPEAT_MIRROR);
			break;
		default: {
		}
	}
}
Viewport::DefaultCanvasItemTextureRepeat Viewport::get_default_canvas_item_texture_repeat() const {