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', 'bh66is1htsh20mfkfmptjcmsp0', '216.73.216.63', '1774510965', '1774510965', '/index.php?XTCsid=7f3d063595fd0cf7dd24ecea4b1409d6&cat=c6_Foodstuffs.html')

[XT SQL Error]