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', 'hqmt4emae2tfhg23oqnc3h6g07', '18.97.9.169', '1771364829', '1771364829', '/xtshop/index.php')

[XT SQL Error]