Thanks for your patience. I have tested the scenario using attached document and XML with following code example. I am facing different exception at my end.
at com.aspose.words.net.System.Data.DataRow.getValue(Unknown Source)
Could you please confirm that you are using the same input document and xml? We will then log this issue in our issue tracking system. Thanks for your cooperation.
Document doc = new Document(MyDir + "inner_attribute.rtf");
DataSet dataSet = new DataSet();
dataSet.readXml(MyDir + "in.xml");
ReportingEngine engine = new ReportingEngine();
doc.save(MyDir + "out.docx");