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', 'pttntej0ou3v5t6u30h1cpaql3', '216.73.216.9', '1758178931', '1758178931', '/index.php?XTCsid=1455d70b156c4853db961f68b595bbe7&cat=c4_Beer-Mugs.html')

[XT SQL Error]