Inno Setup program Im getting a run error using 6.2.2 Access Violation

Question

In this code I'm getting Run time error Exception Access Violation at address 00901E9C Execution of address 00901E9C when it hit objNodes.item(0).setAttribute(xAttrib, xAttribSetValue); Any help will be grateful.

 function ConfigXMLSettingsXAttrib(xpath, xmlFile, xAttrib, xAttribSetValue: String): Boolean;
    var
      XMLDoc, objNodes: Variant;
    begin
      Result := False;

    XMLDoc := GetXMLDocInstance(xmlFile);

    if not VarIsEmpty(XMLDoc) and not VarIsNull(XMLDoc) then
    begin
      objNodes := XMLDoc.selectNodes(xpath);
      try
      if not VarIsEmpty(objNodes) and (objNodes.Length > 0) then
      begin
        if not VarIsNull(objNodes.item(0)) then
        begin
          objNodes.item(0).setAttribute(xAttrib, xAttribSetValue);
          Result := True;
        end
       
      end
      except
       Log(''Unable to set xpathsetvalue)
    end;

    XMLDoc.Save(xmlFile);
  end;
end;