Break out of the loop when iter->Next() fails (nil parent problem in the content iterator).

      result = mTracker->GetPrimaryFrameFor(content, &frame);

      if (NS_SUCCEEDED(result) && frame)

         frame->SetSelected(aRange,aFlags,PR_TRUE);//spread from here to hit all frames in flow

      iter->Next();

      result = iter->Next();

      if (NS_FAILED(result))

      	break;

    }

  }

  return result;