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', '8qi60sfbt701k1qu2ndok8d4o5', '216.73.217.172', '1790479791', '1790479791', '/index.php?XTCsid=4ee4240d4b859190dc69024e020f83f9')

[XT SQL Error]