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', '99qoslm3qnf1pb8pv1ov9h4ue6', '216.73.216.244', '1752213360', '1752213360', '/index.php?XTCsid=a7653c303bc951a885d15df88af8cab9')

[XT SQL Error]