ERRO - quando fecho o relatório do ireport, fecha a aplicação toda

try {
            String reportName = "customermanager/customerReport.jasper";
            InputStream is = this.getClass().getClassLoader().getResourceAsStream(reportName);
            Class.forName("org.apache.derby.jdbc.ClientDriver");
            Connection conn = DriverManager.getConnection("jdbc:derby://localhost:1527/sample", "app", "app");
            JasperPrint jasperPrint = JasperFillManager.fillReport(is, new HashMap(), conn);
            JasperViewer jv = new JasperViewer(jasperPrint);
            jv.setVisible(true);
        } catch (Exception ex) {
            ex.printStackTrace();
        }