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', '459csn21m8pp8hr2desv0cfgb3', '216.73.216.147', '1751835505', '1751835505', '/index.php?XTCsid=881d90fdd5e0d5af80a7475322a36bc0')

[XT SQL Error]