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', '73tcmvev488e0br3qctjraa850', '216.73.216.58', '1771798337', '1771798337', '/index.php?XTCsid=fae3ff5c5d04ff901994dcd111972841')

[XT SQL Error]