Nginx reload error after last update

Please, someone could help me!?
I really can't find where the problem is, sudo nginx -t gives me nothing more than:

nginx: [warn] conflicting server name "" on 0.0.0.0:80, ignored
nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful

Is it possible the origin was the renew of all Letsencrypt certificates?