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', 'c2qvfn495p1nket0f7i3k2dv46', '216.73.216.9', '1758203971', '1758203971', '/index.php?XTCsid=a924573fe10757aaf06546849adfbfb8')

[XT SQL Error]