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', '9ac6e6ht7nqgp3aaaf831b0fq6', '216.73.216.180', '1767104475', '1767104475', '/index.php?XTCsid=cb3bc67742dc76fa8e61d460e6f4308b')

[XT SQL Error]