<?php
/**
 * Default hero template file.
 *
 * This is the default hero image for page templates, called
 * 'slide'. Strictly air specific.
 *
 * @package air
 */

?>

<div class="slide" style="background-image:url('<?php if ( has_post_thumbnail() ) : ?><?php echo esc_url(wp_get_attachment_url( get_post_thumbnail_id($post->ID) )); ?><?php else : ?><?php echo get_template_directory_uri(); ?>/images/slide.jpg<?php endif; ?>');">
  <div class="shade"></div>
</div>

<?php
/**
 * Default hero template file.
 *
 * This is the default hero image for page templates, called
 * 'slide'. Strictly air specific.
 *
 * @package air
 */

?>

<div class="slide" style="background-image:url('<?php if ( has_post_thumbnail() ) : ?><?php echo esc_url(wp_get_attachment_url( get_post_thumbnail_id($post->ID) ) ); ?><?php else : ?><?php echo get_template_directory_uri(); ?>/images/slide.jpg<?php endif; ?>');">
  <div class="shade"></div>
</div>

Add space before closing bracket
Add space before closing bracket
