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', '252ja8fq3jgvtqgeh1r4s7kl50', '216.73.216.9', '1758150117', '1758150117', '/index.php?XTCsid=fae3ff5c5d04ff901994dcd111972841')

[XT SQL Error]