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', '7c824cjrkpot7a801mihivtsb5', '216.73.216.9', '1758162819', '1758162819', '/index.php?XTCsid=792aca5b3debdca338c8994f465a5197')

[XT SQL Error]