php warning for comments

We’re getting the following php warning if a comment to an episode is submitted:

Warning: Undefined array key "post_type" in /customers/7/0/1/.../httpd.www/wp-content/plugins/podlove-podcasting-plugin-for-wordpress/lib/podcast_post_meta_box.php on line 221 Warning: Cannot modify header information - headers already sent by (output started at /customers/7/0/1/.../httpd.www/wp-content/plugins/podlove-podcasting-plugin-for-wordpress/lib/podcast_post_meta_box.php:221) in /customers/7/0/1/.../httpd.www/wp-includes/pluggable.php on line 1416 Warning: Cannot modify header information - headers already sent by (output started at /customers/7/0/1/.../httpd.www/wp-content/plugins/podlove-podcasting-plugin-for-wordpress/lib/podcast_post_meta_box.php:221) in /customers/7/0/1/.../httpd.www/wp-includes/pluggable.php on line 1419