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', 'nnobqgc7vpm5h8tnf9bhc5s5i4', '216.73.217.39', '1785156751', '1785156751', '/index.php?XTCsid=83b95332d9706650377d77928fa044f3')

[XT SQL Error]