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', '3c2fj4qan2if0sh41uo42r68d4', '216.73.216.63', '1774210759', '1774210759', '/index.php?XTCsid=b0dfbf108bdd98cbc25d5050ce8e376a')

[XT SQL Error]