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', 'ep62qq1d8li51l8q892a0kqna2', '107.22.127.78', '1493220932', '1493220932', '/product_info.php?info=p140_Kuschel-Yeti---0-8l-Waermflasche.html&refID=nlrss')

[XT SQL Error]