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', 'or9bgdu1t2oo489fs6usf0p1m5', '54.156.78.4', '1501238368', '1501238368', '/')

[XT SQL Error]