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', 'ncdg8ul7efifbn8eifevnn6oa6', '216.73.216.9', '1757734389', '1757734389', '/index.php?XTCsid=f6e58886be8011b1d9a8e232c116cb7a&cat=c2_Decoration.html&language=en')

[XT SQL Error]