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', 'oact6slbklei2gf3o9ie7r2ba2', '34.229.76.193', '1558619216', '1558619216', '/index.php?language=en')

[XT SQL Error]