title: I-Report 4.1.1 exporting excel sheet issue
body: <p>When i am exporting my report from jasper, it is getting exported in .xlsx but when the same jrxml is exported from java code it is not getting exported in .xlsx.</p>
  
  <p>The java code is as follows:-</p>
  
  <pre><code>exporterXLS.setParameter(JRXlsExporterParameter.SHEET_NAMES, sheetnames );
  exporterXLS.setParameter(JRXlsExporterParameter.JASPER_PRINT_LIST, list);
  exporterXLS.setParameter(JRXlsExporterParameter.OUTPUT_STREAM, output); 
  exporterXLS.exportReport(); 
  </code></pre>
  
  <p>This code is working for another jrxml which is getting exported in .xlsx</p>