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', '3kkeqc0ng1s256qft0n1b58o21', '216.73.216.244', '1752215044', '1752215044', '/index.php?XTCsid=b0772c7414e5eb4fd5398204b3b57ba5')

[XT SQL Error]