title: Accordion panel appears open, but doesn't show content
body: <p>I want to show the first tab, and by default (I mean, without <code>activeIndex</code>) it shows me that tab, but it doesn't show the content.</p>
  
  <pre><code>&lt;p:accordionPanel id="acordeon" value="#{editarReporteExcelBean.reporteOperacionDtoList}" var="reporteOperacion" activeIndex="0" &gt;
      &lt;p:tab id="areaTab" &gt;
          &lt;f:facet name="title"&gt;Area #{reporteOperacion.area.nombre}&lt;/f:facet&gt;
          &lt;anglosgi:reporteOperacion id="reporteOperacion1"
                              reporteOperacionDto="#{reporteOperacion}"
                              formId="reporteForm"
                              contenedorId="reporteForm:acordeon"/&gt;
      &lt;/p:tab&gt;
  &lt;/p:accordionPanel&gt;
  </code></pre>
  
  <p>and there's the first lines of {#reporteOperacion}:</p>
  
  <pre><code>&lt;composite:interface&gt;
          &lt;composite:attribute name="reporteOperacionDto" required="true" /&gt;
          &lt;composite:attribute name="contenedorId" required="true" /&gt;
          &lt;composite:attribute name="formId" required="true" /&gt;
      &lt;/composite:interface&gt;
  
      &lt;composite:implementation&gt;
  
          &lt;p:outputPanel id="panelGeneral" &gt;
  
              &lt;fieldset&gt;
                  &lt;legend&gt;Reporte 
                      &lt;h:outputText value="#{cc.attrs.reporteOperacionDto.metaArchivoReporte.fecha}" &gt;
                          &lt;f:convertDateTime pattern="dd/MM/yyyy" timeZone="GMT-4" /&gt;
                      &lt;/h:outputText&gt;
                  &lt;/legend&gt;
  </code></pre>