if (rowCount > 0)
if (rowCount > 0 && sheet.getRow(0) != null)
    public XlsTable(String sheetName, HSSFSheet sheet) throws DataSetException    {        int rowCount = sheet.getLastRowNum();        if (rowCount > 0)        {            _metaData = createMetaData(sheetName, sheet.getRow(0));        }        else        {            _metaData = new DefaultTableMetaData(sheetName, new Column[0]);        }        _sheet = sheet;    }