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', 't6plcqf55ug9id69hosla6k8o2', '216.73.216.60', '1760549078', '1760549078', '/shop_content.php?XTCsid=ca28ab8f46bb6e791b42fe9b92719761&coID=8')

[XT SQL Error]