I am not sure but try this global:

sub {
# Displays the Father categories.
my ($output,$sth,$cat);
my $cat_db = $DB->table('Category');
$cat_db->select_options ("ORDER BY $CFG->{build_category_sort}") if ($CFG->{build_category_sort});
$sth = $cat_db->select ( { FatherID => 0 } );
$root = [{}];
while (my $cat = $sth->fetchrow_hashref) {
$output .= Links::SiteHTML::display ('print_cat', $root );
}
return $output;
}

Regards
Abd

http://www.idleb.com