get_sites_with_external_nameservers.sh: don't recognize sites with undetermined autoritativ nameservers.

get_sites_with_external_nameservers.sh

@@ -691,14 +691,17 @@ if [[ ${#vhost_config_files_arr[@]} -gt 0 ]]; then
 
          authorited_ns_servers="$(dig +short $_name NS)"
 
+         _error=false
          while [[ -z "$authorited_ns_servers" ]] ; do
             _name="${_name#*.}"
             authorited_ns_servers="$(dig +short $_name NS)"
             if [[ ! "$_name" =~ \. ]]; then
                error "Cannot detect authoritativ nameserver for \033[1m$_site_name\033[m"
+               _error=true
                break
             fi
          done
+         $_error && continue
 
          _found=false
          for _ns_name in $authorited_ns_servers ; do