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', '9fthldtkk5om90ien5lg2g51m6', '216.73.216.85', '1773368926', '1773368926', '/product_info.php?XTCsid=1455d70b156c4853db961f68b595bbe7&info=p16_Octoberfest-CD.html')

[XT SQL Error]