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', 'gtnfp66tgrm18q702eun92qs86', '216.73.216.87', '1765683635', '1765683635', '/index.php?XTCsid=c60d173e05a16d5feea88bc4b1883fc9')

[XT SQL Error]