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', 'ak8g3l5q3pc91efu2jlp9vd706', '216.73.216.180', '1767101842', '1767101842', '/shop_content.php?XTCsid=ec23ca965190a8290c666be9c9947acd&coID=3')

[XT SQL Error]