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', 'es9v1rbjp1pa3e8edlrc1o70r2', '216.73.216.180', '1766143365', '1766143365', '/index.php?XTCsid=a8663af27fecd6867bc12c9550d32100')

[XT SQL Error]