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', '38c26lstltrbpdo83lbvid20t2', '216.73.216.155', '1767504445', '1767504445', '/index.php?XTCsid=a63f52844b6e675f480eaf86612536c2&cat=c12_Music.html')

[XT SQL Error]