Hi!
I am not sure to understand what you intend to do.
If you just switched the 2 code blocks, the parent theme file is not read. The correct code would be:
// theme
if (file_exists($file = ($template = get_template_directory()) .'/wpml-config.xml'))
$this->xml_parse(file_get_contents($file), get_template());
// child theme
if ( $template != ($stylesheet = get_stylesheet_directory()) && file_exists($file = $stylesheet.'/wpml-config.xml'))
$this->xml_parse(file_get_contents($file), get_stylesheet());
Is it what you did?
You can also have a custom wpml-config.xml in wp-content/polylang (you have to create the directory) and this one is the latest loaded.