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', '44f2d9pq00rd4svv8d9u1jmkp3', '216.73.216.178', '1775406764', '1775406764', '/xtshop/index.php?cat=c63_.html')

[XT SQL Error]