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', 'ke7t0n9an7ihmhjdf6ljc219c4', '216.73.216.197', '1751515635', '1751515635', '/index.php?XTCsid=57fdea81df9a3fe5bfa030cad2c80d0c')

[XT SQL Error]