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', '4glg2t4liu50stv2qt1osq5t76', '216.73.216.244', '1752207958', '1752207958', '/index.php?cat=c5_Crockery.html&XTCsid=38f09672db884903e3803adf9d076819')

[XT SQL Error]