Undefined Variables in my PHP embed code

I didn’t notice this until WP DEBUG was set to true, but I noticed two undefined variables when I embedded my bookmark / favorite in my single template (using The Events Calendar, but it shouldn’t really matter). I embedded this code:

<?php the_favorites_button($post_id, $site_id); ?>

And got back these two errors:

Notice: Undefined variable: post_id in /home/hellod8/public_html/wp-content/themes/dadventure/tribe-events/single-event.php on line 39

Notice: Undefined variable: site_id in /home/hellod8/public_html/wp-content/themes/dadventure/tribe-events/single-event.php on line 39

The bookmark does show up, which is great but I would like to address this because who really wants an error?

The page I need help with: [log in to see the link]