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', 'em0r0mbs7fakq0tdde9hpt6g54', '54.144.16.135', '1529319961', '1529319961', '/')

[XT SQL Error]