Error Message When CLick

Hi
I get the error message below when I goto

Home » Administration » Structure » Message types

Notice: Undefined index: message_type_edit_message_type_email_form in drupal_retrieve_form() (line 763 of /home/content/64/3621064/html/DanceSurf/includes/form.inc).
Warning: call_user_func_array() expects parameter 1 to be a valid callback, function 'message_type_edit_message_type_email_form' not found or invalid function name in drupal_retrieve_form() (line 798 of /home/content/64/3621064/html/DanceSurf/includes/form.inc).

Many Thanks for you help :)