Canceling account. Integrity constraint violation: Duplicate entry

I get an error when I try to withdraw an invite.

To recreate:

1. I create an invitation
2. I press "Show Link"
3. I click "Pending" in the menu.
4. The invite show, and I press withdraw
5. Confirm withdraw

An AJAX HTTP error occurred. HTTP Result Code: 500 Debugging information follows. Path: /batch?id=32&op=do StatusText: Service unavailable (with message) ResponseText: 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] => 33 [: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:"contact";i:1;} ) in drupal_write_record() (line 6975 of /[local path]/includes/common.inc).