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', '0l9dlud9s3if4ocp8f9diquel0', '216.73.216.9', '1758099130', '1758099130', '/index.php?XTCsid=fee111602053381265bc5ad0a64c84d2&cat=c6_Foodstuffs.html')

[XT SQL Error]