Seeing the same, looks like it might be the parent::WP_WIdget call on line 9 of: /plugins/yet-another-related-posts-plugin/classes/YARPP_Widget.php
These are the constructor calls which are flagged according to the gist @luciendub posted above:
WP_Widget::WP_Widget()
parent::WP_Widget()
{object}->WP_Widget()