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', '8kodu6sqm36cai93jcsav6dtk2', '107.22.127.78', '1493220903', '1493220903', '/product_info.php?info=p639_Das-Schlaf--Hardcover-.html')

[XT SQL Error]