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', 'elq88avljtacr0q0f1jlicdtk5', '216.73.216.185', '1752882696', '1752882696', '/index.php?cat=c4_Beer-Mugs.html&XTCsid=a63f52844b6e675f480eaf86612536c2')

[XT SQL Error]