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', '40l3hbd4a5r213h2mm0kvep5c0', '216.73.216.180', '1766143990', '1766143990', '/index.php?XTCsid=a63f52844b6e675f480eaf86612536c2&cat=c6_Foodstuffs.html')

[XT SQL Error]