lynda-05-wordpress_building_child_themes/sidebar-footer.php

<?php
/**
 * The sidebar containing the main widget area.
 *
 * @link https://developer.wordpress.org/themes/basics/template-files/#template-partials
 *
 * @package popper
 */

if ( ! is_active_sidebar( 'sidebar-foooter' ) ) {
	return;
}
?>

<div id="tertiary" class="widget-area clear" role="complementary">
	<?php dynamic_sidebar( 'sidebar-foooter' ); ?>
</div><!-- #secondary -->