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', '8n2h6kir1dk1jeelnd884v9nh2', '216.73.216.145', '1778251890', '1778251890', '/index.php?XTCsid=a70ff5bef6ed3980b6a8b7590f98adca')

[XT SQL Error]