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', '3u124vcl1fqp2lq3qa3m2to5r6', '54.162.109.90', '1495804308', '1495804308', '/shop_content.php?coID=13&page=20')

[XT SQL Error]