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', 'e8o6uvep9b6birc8517amafs50', '216.73.216.9', '1757989100', '1757989100', '/index.php?XTCsid=d3f81aac1b90a5822d8663a3af39931e&cat=c6_Foodstuffs.html&language=en')

[XT SQL Error]