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', 'b364542ninir4j3mk3rif2rhl7', '216.73.216.60', '1760371606', '1760371606', '/product_info.php?XTCsid=c5d9d9a5780af7d5707e3b2046ece3fe&info=p16_Octoberfest-CD.html&language=de')

[XT SQL Error]