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', 'gkcj8cakiui0aiiods9021rol5', '34.229.76.193', '1558618836', '1558618836', '/shop_content.php?coID=1')

[XT SQL Error]