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', '9nr4u9v0hci5ludnf8tnqpcn42', '216.73.216.9', '1757990320', '1757990320', '/index.php?XTCsid=d8fb38e8fa3ae8ffd83e3fe617bdce5f')

[XT SQL Error]