Modify content template when no image is uploaded

<?php
// http://www.gravityhelp.com/forums/topic/make-an-image-a-link-in-post-template
// change the 171 here to your actual form ID
add_action('gform_pre_submission_filter_171', 'change_post_content_template');
function change_post_content_template($form) {
        // if input_5 is submitted, i.e. has an image, then insert the HTML into the content template.  Otherwise, just use {Details:2}
        // check the $_FILES global since it's an image upload
        if ((!isset($_FILES['input_5']['name']) || $_FILES['input_5']['name'] == null)) {
                $form['postContentTemplate'] = '{Details:2}';
        }
        else {
                // use a PHP heredoc to preserve line breaks
                $template = <<<EOT
<a href='{Image:5:large:url}'>{Image:5:listing:right}</a>

{Details:2}
EOT;
                $form['postContentTemplate'] = $template;
        }
        // return the modified form object
        return $form;
}