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', '51ir5squgv9j4kdv2bg0ldl9n0', '54.162.109.90', '1495803954', '1495803954', '/shop_content.php?coID=9&watch=1063')

[XT SQL Error]