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', 'b9ljdik4su82dn9tfroev5uir1', '216.73.216.28', '1765209528', '1765209528', '/index.php?XTCsid=a0c8d0b3d08cb472c84559a313755d47&cat=c6_Foodstuffs.html')

[XT SQL Error]