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', 'ke3cfvb9h9d932fu43hu1qb5m1', '216.73.216.70', '1752613815', '1752613815', '/index.php?XTCsid=8c15d273183189e5e8d39cad65237995')

[XT SQL Error]