Issue on Themes

Good evening, I updated my version of WP to 6.0, first I deactivated the plugins and then reactivated one by one and updated those too, the site is reachable and works correctly but when I try to access some pages of the site I get the following error message : Warning: Creating default object from empty value in /home/vc4y0518/public_html/wp-content/themes/ati/functions.php on line 315 Specifically this is what is present in line 315: function close_comments( $posts ) { if ( !is_single() ) { return $posts; } if ( time() - strtotime( $posts[0]->post_date_gmt ) > ( 30 * 24 * 60 * 60 ) ) { $posts[0]->comment_status = 'closed'; $posts[0]->ping_status = 'closed'; } return $posts; Can you help me? Thank you