1366 - Incorrect integer value: '' for column 'customer_id' at row 1

insert into whos_online (customer_id, full_name, session_id, ip_address, time_entry, time_last_click, last_page_url) values ('', 'Guest', '9gi1hneh5bok66tjujnt1uceb5', '216.73.217.89', '1789598467', '1789598467', '/index.php?XTCsid=5771d82eee0b9754fa5c3ca98fd4f740')

[XT SQL Error]