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', 'u79t1s3q7ge5grfg3be9n711j3', '216.73.216.121', '1761845004', '1761845004', '/index.php?XTCsid=afb4a1ae80caf4f0a7d531c4b0a5325b')

[XT SQL Error]