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', 'm3cjlcbp8cni175f44ffn1gb21', '216.73.216.63', '1774441820', '1774441820', '/index.php?XTCsid=363052f8eb28c495db1ddeca225278d6&cat=c4_Beer-Mugs.html')

[XT SQL Error]