title: PrimeFaces Self-updated required Picklist with AJAX transfer event does not remove all items
body: <p>I have a simple <code>&lt;p:pickList&gt;</code> that also has an AJAX "transfer" event pointed to an empty event on my backing bean and tagged as required. When the user clicks in the Remove, all button the target list only "blinks", then remains the same (unaltered). All other buttons work properly.</p>
  
  <p>PrimeFaces 4.0.</p>
  
  <p>If the <code>&lt;p:pickList&gt;</code> is not required or does not update itself, everything keeps fine.</p>
  
  <p>Is this some kind of bug?</p>
  
  <p>Thanks!!!</p>
  
  <hr>
  
  <pre><code>&lt;p:pickList id="nivelPickListTeste" 
      value="#{cargoBean.niveis}" 
      var="nivel" 
      required="true" 
      requiredMessage="O campo de niveis selecionados é obrigatório."
      itemValue="#{nivel}" 
      itemLabel="#{nivel.codigo}" 
      converter="nivelDualListConverter"&gt;
      &lt;p:ajax event="transfer" listener="#{cargoBean.onTransfer}" update="@this" /&gt;
      &lt;p:column styleClass="linhatabela negrito"&gt;
      &lt;h:outputText value="#{nivel.codigo} - #{nivel.formatarValor()}" /&gt;
      &lt;/p:column&gt;
  &lt;/p:pickList&gt;
  </code></pre>
  
  
  
  <pre><code>public class CargoBean {
      public void onTransfer(TransferEvent event) {}
  }
  </code></pre>