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', 'e1gi84nukibqhgptjlji6g64f7', '216.73.216.87', '1765904469', '1765904469', '/index.php?XTCsid=af985dc333873312cc1dc8aa652474cb')

[XT SQL Error]