Displaying a hierarchical, linked list of category/taxonomy terms in WordPress

I’m having a small issue getting this list of subcategories to display the way I want them to. (Actually, it’s a custom taxonomy in this case, but it’s the same idea.) I have the following code, and it ALMOST works perfectly. I want the parent taxonomy term NOT to be linked but all of the child taxonomy terms to be linked.

For some reason, when I use get_category_link( $cat->term_id ), it doesn’t return anything at all in the link.

<?php
foreach( get_categories('taxonomy=location&hide_empty=false') as $cat ) :
if( !$cat->parent ) {
    echo '<ul><li><strong>' . $cat->name . '</strong></li>';
    process_cat_tree( $cat->term_id );
}
endforeach;

wp_reset_query();

function process_cat_tree( $cat ) {
    $args = array('category__in' => array( $cat ), 'numberposts' => -1);
    $cat_posts = get_posts( $args );
    $next = get_categories('taxonomy=location&hide_empty=false&parent=' . $cat);

    if( $next ) :
        foreach( $next as $cat ) :
            echo '<ul><li><a href="' . get_category_link( $cat->term_id ) . '" title="' . sprintf( __( "View all posts in %s" ), $cat->name ) . '" ' . '>' . $cat->name.'</a></li>';
            process_cat_tree( $cat->term_id );
        endforeach;
    endif;

    echo '</ul>';
}
?>

I’m sure it’s my own stupidity, but can anyone enlighten me?