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', '77f15go5p0k55ftgs7o9o0gul3', '216.73.216.9', '1757795143', '1757795143', '/index.php?XTCsid=ec445a26a1be1b54e711876da9fff244&cat=c4_Bierkruege.html')

[XT SQL Error]