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', '52d8s621tt652lo31l3qf9rt47', '216.73.216.175', '1789453455', '1789453455', '/index.php?XTCsid=32bc53310efafffaa756fafd3e8b8712')

[XT SQL Error]