Remove GError parameters from gtk_builder_add_from_file(), gtk_builder_add_from_resource(), and gtk_builder_add_from_string()
The documentation says:
It’s not really reasonable to attempt to handle failures of this call. The only reasonable thing to do when an error is detected is to call g_error().
So GTK should call g_error() itself, instead of giving the application a GError and expecting it to do so manually.