Add a placeholder description if none is set

functions.php

<?php
// Paste the code BELOW this line into your child theme functions.

/**
 * Add a placeholder description if none is set
 *
 * @author Reasons to Use Genesis
 * @link http://reasonstousegenesis.com/site-description/
 */
add_action( 'genesis_site_description', 'rtug_placeholder_description' );
function rtug_placeholder_description() {

	if ( ! esc_html( get_bloginfo( 'description' ) ) )
		echo '<p class="site-description">Just another WordPress site</p>';

}