fixed bulk change nameserver form

app/controllers/repp/v1/registrar/nameservers_controller.rb

@@ -67,7 +67,7 @@ module Repp
         end
 
         def verify_nameserver_existance
-          return true if hostname.nil?
+          return true if hostname.blank?
 
           current_user.registrar.nameservers.find_by!(hostname: hostname)
         end

app/views/registrar/bulk_change/_nameserver_form.html.erb

@@ -3,11 +3,11 @@
 
     <div class="form-group">
         <div class="col-md-2 control-label">
-            <%= label_tag :old_hostname %>
+            <%= label_tag t '.old_hostname' %>
         </div>
 
         <div class="col-md-4">
-            <%= text_field_tag :old_hostname, params[:old_hostname], required: true,
+            <%= text_field_tag :old_hostname, params[:old_hostname], required: false,
                                class: 'form-control' %>
         </div>
     </div>

config/locales/registrar/bulk_change.en.yml

@@ -32,6 +32,7 @@ en:
           ident data ie for updating contact information.
 
       nameserver_form:
+        old_hostname: Old hostname (optional)
         ip_hint: One IP per line
         replace_btn: Replace nameserver
         help_btn: Toggle help