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', '9n0h42b9ifdq3fnct75ao3ckf1', '216.73.216.110', '1752049234', '1752049234', '/index.php?cat=c6_Foodstuffs.html&XTCsid=e6c7e5517e0166a5652a3243f444cf4b')

[XT SQL Error]