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', '4ovpcm2vqnm4p3ef7baruio1t1', '216.73.216.9', '1758002468', '1758002468', '/index.php?XTCsid=3fe9dd652ff9e1094adeb9d805d8e45a')

[XT SQL Error]