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', 'jvi6qutjd2q9nrofh9rfdi68r4', '216.73.217.148', '1780785135', '1780785135', '/xtshop/login.php')

[XT SQL Error]