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', '9lna0fmitjskn672fso5l7efl7', '216.73.216.76', '1789122188', '1789122188', '/product_info.php?XTCsid=a8f768c639dfd62c2d6d3cd7ed21b720&info=p8_100-Placemats.html')

[XT SQL Error]