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', '7r6jq374se6rvj12uteocf76r5', '216.73.216.140', '1763671408', '1763671408', '/shop_content.php?XTCsid=2f0d32e80e0e3a7e9efdd2dc2a571c8d&coID=1')

[XT SQL Error]