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', '1i469461nccaplgjs8hjrbsl77', '216.73.216.9', '1757916771', '1757916771', '/shop_content.php?XTCsid=9265b55633a2cb4e8ed6db3536c73ca5&coID=1')

[XT SQL Error]