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', 'i6merm2kmhk6hiopucl7mb5du4', '216.73.216.180', '1766571533', '1766571533', '/popup_content.php?XTCsid=f9686763d06aa7254e0b8fc7abce63fb&coID=1')

[XT SQL Error]