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', '1ubg6tn33r5p5h7dcsmr4ae8h5', '216.73.216.63', '1774270752', '1774270752', '/index.php?XTCsid=a8f768c639dfd62c2d6d3cd7ed21b720&cat=c5_Crockery.html')

[XT SQL Error]