error 500 when javascript is disabled

Hi dev,

When javascript is disabled ( /?PageSpeed=noscript at the end of url) , i found an issue when i put this code on my single.php :
<?php wp_related_posts(); ?>

It gets error 500.

With or Without javascript disabled it works only in this case: when the option
Auto Insert Related Posts (or add <?php wp_related_posts()?> to your single post template) is activated.

How to fix it for javascript disabled? here is my website http://www.seeyar.fr

thank you

https://wordpress.org/plugins/wordpress-23-related-posts-plugin/