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', '2pkn95drcshomnhprck8ol0m42', '216.73.216.174', '1762429823', '1762429823', '/xtshop/login.php')

[XT SQL Error]