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', 'j6l4s4l60t30ti28qtq940pf60', '216.73.216.63', '1773906881', '1773906881', '/index.php?XTCsid=8d868f90067cee2351b383dfcfd75af4')

[XT SQL Error]