[Theme: Thematic] List custom taxonomy terms in child theme

I have custom post type “products” and custom taxonomy “products_categories”.
I want to display all “products_categories” on custom page “page-offer.php”.

I’ve put this code under the_content() tag:

//list terms in a given taxonomy (useful as a widget for twentyten)
$taxonomy = 'products_categories';
$tax_terms = get_terms($taxonomy);
?>
<?php
foreach ($tax_terms as $tax_term) {
echo '<li>' . '<a href="' . esc_attr(get_term_link($tax_term, $taxonomy)) . '" title="' . sprintf( __( "View all posts in %s" ), $tax_term->name ) . '" ' . '>' . $tax_term->name.'</a></li>';
}

And I get nothing! It’s problem with global variables?

http://wordpress.org/extend/themes/thematic/