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', '4a9i27icn4ijtv7c2k6adtn5s2', '216.73.216.244', '1752216625', '1752216625', '/index.php?cat=c12_Music.html&XTCsid=6c2468ca28c6c182aaed37353d32ae32')

[XT SQL Error]