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', 'p2pss36qc3m9nsh91jsm3ogmj3', '54.144.14.128', '1498168984', '1498168984', '/')

[XT SQL Error]