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', 'i5iu4r141c6imejientbqci152', '54.224.255.158', '1498515354', '1498515354', '/product_info.php?info=p140_Kuschel-Yeti---0-8l-Waermflasche.html&refID=nlrss')

[XT SQL Error]