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', 'qsqke4urbi244ctck2014kn9j4', '216.73.216.147', '1751737835', '1751737835', '/index.php?cat=c5_Crockery.html&XTCsid=a8f768c639dfd62c2d6d3cd7ed21b720')

[XT SQL Error]