Error on city delete

When I delete a city the page redirects and i get this message:

Warning: call_user_func_array() expects parameter 1 to be a valid callback, class 'DevB_Blog_Comment_Notifier' does not have a method 'post_deleted' in /homepages/10/d526297926/htdocs/wp-includes/plugin.php on line 525

Warning: Cannot modify header information - headers already sent by (output started at /homepages/10/d526297926/htdocs/wp-includes/plugin.php:525) in /homepages/10/d526297926/htdocs/wp-includes/pluggable.php on line 1228

Please note this is in GD -> MultiLocations -> Manage Location.

The location is however deleted on page refresh.

Not sure what is happening, you can test and delete the locations leeds (NOT LIVERPOOL).

Thanks UF