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', 'c773uiifr3qj7ffoub4qficac1', '216.73.216.76', '1789065862', '1789065862', '/index.php?XTCsid=4a177549c6a71de0023f5e2b49c3e919')

[XT SQL Error]