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', '6lvildhniatujesbgj2iuf9o31', '216.73.216.180', '1767308846', '1767308846', '/index.php?XTCsid=6ea716b38374b85491957cc78c31f210')

[XT SQL Error]