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', '0nmqtouugt5b9c4m18c62pmk25', '216.73.216.147', '1751964451', '1751964451', '/index.php?cat=c6_Foodstuffs.html&XTCsid=705a3b68bece48fd9b67e5e30d623e8e')

[XT SQL Error]