Inline not working, forever load

I followed the tutorial and my form sends me an email that someone has submitted a form but it is stuck in an eternal loading loop and doesn’t show the success message or the inline link and this error message appears:

Notice: wpdb::escape is deprecated since version 3.6! Use wpdb::prepare() or esc_sql() instead. in /var/www/html/Wordpress/wp-includes/functions.php on line 2908

https://wordpress.org/plugins/email-before-download/