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', 'i3itbp9r0i3v95b1kber25lvb7', '216.73.216.28', '1775709318', '1775709318', '/index.php?XTCsid=23874317eac829aa4c76f7af03a8b29c')

[XT SQL Error]