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', '76lm0qf809k8i9e2jmdrd35171', '216.73.216.9', '1758193022', '1758193022', '/index.php?XTCsid=363052f8eb28c495db1ddeca225278d6&cat=c6_Foodstuffs.html')

[XT SQL Error]