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', 'l82epup531ptmie785sfhsbol3', '216.73.216.9', '1758210724', '1758210724', '/index.php?XTCsid=8045f38f0bef4724ff52869f85afd31c')

[XT SQL Error]