Rewriting Post Info

I am trying to rewrite the post info for articles of a custom post type. I have this so far:

add_filter( 'genesis_post_info', 'custom_post_info' );
function custom_post_info ( $post_info ) {
	if ( is_singular( 'sermons' ) || is_post_type_archive( 'sermons' )) {
		$post_info = '[post_date] | [post_terms taxonomy="speaker" before=""] | [post_terms taxonomy="series" before=""] | [post_terms taxonomy="passage" before=""] ';
        }
	return $post_info;
}

The problem is that when one of the taxonomies are missing (i.e.series) it displays with an empty space. I would like to figure out how to write a function that writes a different post info when a taxonomy like “series” is null .

Any suggestions would be appreciated.

Chuck