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', '1h1lo8hr0ueg04npl9gu17n3c7', '216.73.216.9', '1758004110', '1758004110', '/index.php?XTCsid=1ea6ae83a06864ae88742e98ecbda16e&cat=c4_Beer-Mugs.html')

[XT SQL Error]