### 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(false);
	return handle_input_locally;
}
void Viewport::set_default_canvas_item_texture_filter(DefaultCanvasItemTextureFilter p_filter) {
	ERR_MAIN_THREAD_GUARD;
	ERR_FAIL_INDEX(p_filter, DEFAULT_CANVAS_ITEM_TEXTURE_FILTER_MAX);
	if (default_canvas_item_texture_filter == p_filter) {
		return;
	}
	default_canvas_item_texture_filter = p_filter;
	switch (default_canvas_item_texture_filter) {
		case DEFAULT_CANVAS_ITEM_TEXTURE_FILTER_NEAREST:
			RS::get_singleton()->viewport_set_default_canvas_item_texture_filter(viewport, RS::CANVAS_ITEM_TEXTURE_FILTER_NEAREST);
			break;
		case DEFAULT_CANVAS_ITEM_TEXTURE_FILTER_LINEAR:
			RS::get_singleton()->viewport_set_default_canvas_item_texture_filter(viewport, RS::CANVAS_ITEM_TEXTURE_FILTER_LINEAR);
			break;
		case DEFAULT_CANVAS_ITEM_TEXTURE_FILTER_LINEAR_WITH_MIPMAPS:
			RS::get_singleton()->viewport_set_default_canvas_item_texture_filter(viewport, RS::CANVAS_ITEM_TEXTURE_FILTER_LINEAR_WITH_MIPMAPS);
			break;
		case DEFAULT_CANVAS_ITEM_TEXTURE_FILTER_NEAREST_WITH_MIPMAPS:
			RS::get_singleton()->viewport_set_default_canvas_item_texture_filter(viewport, RS::CANVAS_ITEM_TEXTURE_FILTER_NEAREST_WITH_MIPMAPS);
			break;
		default: {
		}
	}
}
Viewport::DefaultCanvasItemTextureFilter Viewport::get_default_canvas_item_texture_filter() const {