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', '6hst3tsdn6utnscsp6l8llpj56', '216.73.216.28', '1765024723', '1765024723', '/index.php?XTCsid=e65207aee44f142683bacdd3544c84a8&language=en')

[XT SQL Error]