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', '8ltl5p2nid5u43de5per811cv2', '216.73.216.121', '1761837919', '1761837919', '/shop_content.php?XTCsid=9265b55633a2cb4e8ed6db3536c73ca5&coID=2')

[XT SQL Error]