message: don't crash if trying to load a transfer function from a file fails
diff: @@ -331,10 +331,14 @@ void TransferFunction::render()
  void TransferFunction::load(const ospcommon::FileName &fileName)
  {
  + try {
  tfn::TransferFunction loaded(fileName);
  transferFunctions.emplace_back(fileName);
  tfcnSelection = transferFunctions.size() - 1;
  setColorMap(true);
  + } catch (const std::runtime_error &e) {
  + std::cerr << "ERROR: " << e.what() << std::endl;
  + }
  }
  void TransferFunction::save(const ospcommon::FileName &fileName) const
  