Error on updating existing relationship

When changing the name of my one relationship, the site gave the following error:

PDOException: SQLSTATE[HY000]: General error: 1366 Incorrect integer value: '' for column 'rtid' at row 1: INSERT INTO {user_relationship_limits} (rid, rtid, role_limit) VALUES (:db_insert_placeholder_0, :db_insert_placeholder_1, :db_insert_placeholder_2); Array ( [:db_insert_placeholder_0] => 1 [:db_insert_placeholder_1] => [:db_insert_placeholder_2] => 0 ) in user_relationship_limits_submit() (line 254 of .../sites/all/modules/user_relationship_limits/user_relationship_limits.module).

Looks like the rtid is not sent along while editing?