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', 't86phhtgb4m5a209k7su75tj22', '216.73.216.130', '1760800919', '1760800919', '/shop_content.php?XTCsid=363052f8eb28c495db1ddeca225278d6&coID=8')

[XT SQL Error]