Bug when an anonymous invite someone

Hi

There is a bug when anonymous invite someone. This email was already invited before

I have big error message. I am using drupal 7.9

PDOException : SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '' for key 'name': INSERT INTO {users} (uid, name, pass, mail, theme, signature, signature_format, created, access, login, status, timezone, language, picture, init, data) VALUES (:db_insert_placeholder_0, :db_insert_placeholder_1, :db_insert_placeholder_2, :db_insert_placeholder_3, :db_insert_placeholder_4, :db_insert_placeholder_5, :db_insert_placeholder_6, :db_insert_placeholder_7, :db_insert_placeholder_8, :db_insert_placeholder_9, :db_insert_placeholder_10, :db_insert_placeholder_11, :db_insert_placeholder_12, :db_insert_placeholder_13, :db_insert_placeholder_14, :db_insert_placeholder_15); Array ( [:db_insert_placeholder_0] => 59 [:db_insert_placeholder_1] => [:db_insert_placeholder_2] => [:db_insert_placeholder_3] => [:db_insert_placeholder_4] => [:db_insert_placeholder_5] => [:db_insert_placeholder_6] => [:db_insert_placeholder_7] => 0 [:db_insert_placeholder_8] => 0 [:db_insert_placeholder_9] => 0 [:db_insert_placeholder_10] => 0 [:db_insert_placeholder_11] => [:db_insert_placeholder_12] => [:db_insert_placeholder_13] => 0 [:db_insert_placeholder_14] => [:db_insert_placeholder_15] => a:1:{s:7:"invites";i:9;} ) dans drupal_write_record() (ligne 6884 dans /home/www/drupal-7.9/includes/common.inc).