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', 'd2e6cac71061631fa998db6406fda9a9', '216.73.216.190', '1776276486', '1776276486', '/shop/product_info.php?info=p115_.html')

[XT SQL Error]