Fix mail argument check in v-add-letsencrypt-domain

bin/v-add-letsencrypt-domain

@@ -67,7 +67,8 @@ check_args '2' "$#" 'USER DOMAIN [ALIASES] [MAIL]'
 is_format_valid 'user' 'domain' 'aliases'
 is_object_valid 'user' 'USER' "$user"
 is_object_unsuspended 'user' 'USER' "$user"
-if [ -z "$mail" ]; then
+if [[ -z "${mail// }" ]] || [ "$mail" = 'no' ]; then
+    mail=''
     is_system_enabled "$WEB_SYSTEM" 'WEB_SYSTEM'
     is_object_valid 'web' 'DOMAIN' "$domain"
     is_object_unsuspended 'web' 'DOMAIN' "$domain"