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', '40v6k3acuitiok23ilb4tijoc2', '216.73.216.122', '1767890168', '1767890168', '/shop_content.php?XTCsid=38717c4dd62e88001622b2c7b8b8372a&coID=1')

[XT SQL Error]