IReport + JSF + PrimeFaces - Problema ao exibir o report gerado usando Primefaces media

<p:dataTable id="amostraDataTable" var="amostra"
                    value="#{searchAmostraBean.amostraList}" paginator="true" rows="10"
                    paginatorTemplate="     "
                    rowsPerPageTemplate="5,10,15"
                    emptyMessage="A pesquisa não retornou resultados"
                    paginatorPosition="bottom">

                    <p:column style="width: 184px;height: 50px;">
                        <f:facet name="header">
                            <p:commandLink id="create" action="pretty:createAmostra"
                                title="Novo">
                                <h:graphicImage value="/images/btn_novo.png" />
                            </p:commandLink>
                        </f:facet>
                        <p:panelGrid columns="3" style="width: 40px;height: 30px;">
                            <pretty:link mappingId="changeAmostra" title="Editar">
                                <f:param value="#{amostra.id}" />
                                <h:graphicImage value="/images/btn_editar.png" />
                            </pretty:link>
                            <pretty:link mappingId="removeAmostra" title="Apagar">
                                <f:param value="#{amostra.id}" />
                                <h:graphicImage value="/images/btn_apagar.png" />
                            </pretty:link>
                            <pretty:link mappingId="visualizeAmostra" title="Ver">
                                <f:param value="#{amostra.id}" />
                                <h:graphicImage value="/images/btn_ver.png" />
                            </pretty:link>
                            <p:commandButton id="gerarPdf" value="gerar pdf" rendered="true"
                                oncomplete="PF('reportVar').show();" actionListener="#{searchAmostraBean.putAmostra(amostra)}"
                                update=":amostraForm:commonReport :amostraForm:pdfView">
                            </p:commandButton>
                        </p:panelGrid>
                    </p:column>
<!--  resto das linhas ignorado  -->

<p:dialog id="commonReport" resizable="false" draggable="false"
                position="center" width="500" height="300" modal="true"
                header="OCPlus - Etiqueta de rastreio" dynamic="true" 
                widgetVar="reportVar" >
                <p:outputPanel id="reportPanel">
                    <p:media id="pdfView" value="#{searchAmostraBean.etiqueta}" width="100%"
                        height="300px" player="pdf" >
                    </p:media>
                </p:outputPanel>
            </p:dialog>

public void putAmostra(Amostra amostra){
        this.amostra = amostra;
    }

    public StreamedContent getEtiqueta(){
        File etiqueta = null;
        InputStream is;
        try {
            ArrayList<Amostra> listAmostra = new ArrayList<Amostra>();
            listAmostra.add(amostra);
            JRBeanCollectionDataSource jrBeanCollectionDataSource = new JRBeanCollectionDataSource(listAmostra);
            JasperPrint jasperPrint = JasperFillManager.fillReport(reportPath, new HashMap<String,Object>(),jrBeanCollectionDataSource);
            JRExporter exporter = new JRPdfExporter();
            etiqueta =new File("OCPlusTicket_"+amostra.getNumero().toString());

            exporter.setParameter(JRExporterParameter.JASPER_PRINT, jasperPrint);
            exporter.setParameter(JRExporterParameter.OUTPUT_FILE, etiqueta);
            exporter.exportReport();

            is = new FileInputStream(etiqueta);
            etiqueta.deleteOnExit();
            DefaultStreamedContent sc = new DefaultStreamedContent(is,"application/pdf","OCPlusTicket_"+amostra.getNumero().toString());
            return sc;
        } catch (JRException | FileNotFoundException e ) {
            e.printStackTrace();
            return null;
        }

    }