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', '4bomfig4u9j3esismft8b34pp2', '216.73.216.9', '1757837868', '1757837868', '/index.php?XTCsid=25107e022e57904016ff1d84720d2d85')

[XT SQL Error]