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', 'atf9h1n9cti1dcf2pnrf993906', '216.73.216.9', '1757794418', '1757794418', '/index.php?XTCsid=69b3fcc0fb5a34f08b494675bac7e6ec')

[XT SQL Error]