Erro Log on YarPP

Hello

Does anyone have any idea what this error is all about?
Having some problems trying to find it.
Found in our error logs.

[18-Aug-2014 05:42:52 UTC] PHP Stack trace:
[18-Aug-2014 05:42:52 UTC] PHP 1. {main}() /home/cmcm1461/public_html/index.php:0
[18-Aug-2014 05:42:52 UTC] PHP 2. require() /home/cmcm1461/public_html/index.php:17
[18-Aug-2014 05:42:52 UTC] PHP 3. require_once() /home/cmcm1461/public_html/wp-blog-header.php:16
[18-Aug-2014 05:42:52 UTC] PHP 4. do_feed() /home/cmcm1461/public_html/wp-includes/template-loader.php:37
[18-Aug-2014 05:42:52 UTC] PHP 5. do_action() /home/cmcm1461/public_html/wp-includes/functions.php:1095
[18-Aug-2014 05:42:52 UTC] PHP 6. call_user_func_array:{/home/cmcm1461/public_html/wp-includes/plugin.php:470}() /home/cmcm1461/public_html/wp-includes/plugin.php:470
[18-Aug-2014 05:42:52 UTC] PHP 7. do_feed_rss2() /home/cmcm1461/public_html/wp-includes/plugin.php:470
[18-Aug-2014 05:42:52 UTC] PHP 8. load_template() /home/cmcm1461/public_html/wp-includes/functions.php:1127
[18-Aug-2014 05:42:52 UTC] PHP 9. require_once() /home/cmcm1461/public_html/wp-includes/template.php:501
[18-Aug-2014 05:42:52 UTC] PHP 10. the_excerpt_rss() /home/cmcm1461/public_html/wp-includes/feed-rss2.php:81
[18-Aug-2014 05:42:52 UTC] PHP 11. apply_filters() /home/cmcm1461/public_html/wp-includes/feed.php:222
[18-Aug-2014 05:42:52 UTC] PHP 12. call_user_func_array:{/home/cmcm1461/public_html/wp-includes/plugin.php:192}() /home/cmcm1461/public_html/wp-includes/plugin.php:192
[18-Aug-2014 05:42:52 UTC] PHP 13. YARPP->the_excerpt_rss() /home/cmcm1461/public_html/wp-includes/plugin.php:192
[18-Aug-2014 05:42:52 UTC] PHP Notice: Use of undefined constant get_post_type – assumed ‘get_post_type’ in /home/cmcm1461/public_html/wp-content/plugins/yet-another-related-posts-plugin/classes/YARPP_Core.php on line 1467

https://wordpress.org/plugins/yet-another-related-posts-plugin/