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', 'o4uv3tnch9smf46h1jarrk9np1', '216.73.216.139', '1770005395', '1770005395', '/index.php?XTCsid=01e479217619e936c91dd401f6dca485')

[XT SQL Error]