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', '5sqvf22uvs31bqvngp9g8l1b61', '216.73.216.9', '1757836226', '1757836226', '/index.php?XTCsid=4a904474bf526fde816694d0f8d11e7a')

[XT SQL Error]