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', 'k4l4r2lojr520rm581fetkbum2', '216.73.216.110', '1752049484', '1752049484', '/index.php?cat=c6_Foodstuffs.html&XTCsid=4299a8bbf7f56cb5a06703b866244eb3')

[XT SQL Error]