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', '1tnf3am4bmpebqksdsnbd4s3n2', '216.73.216.147', '1781022649', '1781022649', '/product_info.php?XTCsid=4b76b23a7a255ffc6a8ec68c490ddaae&info=p2_Bavarian-Pennant-Chain.html')

[XT SQL Error]