<?php
/**
 * The sidebar containing the main widget areas.
 *
 * @package _s
 */

if ( ! is_active_sidebar( 'sidebar-1' ) )
	return;
?>
	<div id="secondary" class="widget-area" role="complementary">
		<?php dynamic_sidebar( 'sidebar-1' ); ?>
	</div><!-- #secondary -->

<?php
/**
 * The sidebar containing the main widget area.
 *
 * @package _s
 */

if ( ! is_active_sidebar( 'sidebar-1' ) ) {
	return;
}
?>

<div id="secondary" class="widget-area" role="complementary">
	<?php dynamic_sidebar( 'sidebar-1' ); ?>
</div><!-- #secondary -->

Use braces in all conditionals.
_s: Use braces in all conditionals.

Formatting updates for file comment, conditional braces, and indentation.