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', '4r481ddnt1q6d6u8puaqc2e5r3', '216.73.216.80', '1751326864', '1751326864', '/index.php?XTCsid=d8fb38e8fa3ae8ffd83e3fe617bdce5f')

[XT SQL Error]