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', '5t6d6ua0eb3011u0d61anj10t0', '216.73.216.63', '1774416020', '1774416020', '/index.php?XTCsid=69a1e06b1d537d651878c63fe4ee3fec&cat=c12_Music.html')

[XT SQL Error]