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', 'ej1gkvmrm97ap5n6qtf3ef6ep3', '216.73.216.130', '1760851407', '1760851407', '/index.php?XTCsid=6bb5e4d6110a5fe0c19bd41c6b302c38&cat=c5_Crockery.html&language=de')

[XT SQL Error]