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', 'a650umm9mefjbg4drfm32uftb7', '216.73.216.200', '1789478214', '1789478214', '/index.php?XTCsid=654649deb240b955f31e60a99b6f2f28')

[XT SQL Error]