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', '9f2mra8f3374dl9llel4om0v51', '216.73.216.180', '1766011184', '1766011184', '/index.php?XTCsid=2fbe11bab8d79764eb267b19bf7c8336')

[XT SQL Error]