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', 'u6r0nkpohmilfecnbfva2chig0', '216.73.216.70', '1752610381', '1752610381', '/index.php?cat=c8_Disposable-tableware.html&XTCsid=e6c7e5517e0166a5652a3243f444cf4b')

[XT SQL Error]