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', 'h1nd7hv2rmgom43tk789n3end0', '3.15.201.103', '1746876739', '1746876739', '/xtshop/address_book.php')

[XT SQL Error]