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', 'j5vpcvrnmrv5k0sjp5068bea54', '216.73.216.31', '1774979799', '1774979799', '/index.php?XTCsid=3927d66f1162df83a1f40750d6538238')

[XT SQL Error]