PHP WordPress gallery not finding the XMLl file

The code is below – it uses a wordpress shortcode which is [my_hmg=widget.xml] but if you try change the xml file like this [my_hmg=example_gallery.xml] it just always reverts to the default widget.xml

The problem is in the function my_hmg_filter_Callback in particular these 2 lines;

@$my_hmg_file = @$output['filename'];
if($my_hmg_file==""){$my_hmg_file = "widget.xml";}

For some reason it always thinks the file name is blank so always reverts to widget.xml.

The files can be downloaded from here – http://www.gopiplus.com/work/2010/07/18/horizontal-motion-gallery/

function my_hmg_show_filter($content){
    return  preg_replace_callback('/[my_hmg=(.*?)]/sim','my_hmg_filter_Callback',$content);
}


function my_hmg_filter_Callback($matches) 
{
    $my_hmg_package = "";
    $var = $matches[1];
    parse_str($var, $output);

    @$my_hmg_file = @$output['filename'];
    if($my_hmg_file==""){$my_hmg_file = "widget.xml";
}