message: fix leaking of released pixel ops, don't double release world and renderer
diff: @@ -304,6 +304,7 @@ int main(int argc, const char **argv)
  }
  if (!pixelPipeline.empty() && ImGui::Button("Remove Op")) {
  + ospRelease(pixelPipeline.back());
  pixelPipeline.pop_back();
  enabledOps.pop_back();
  debugColors.pop_back();
  @@ -329,8 +330,6 @@ int main(int argc, const char **argv)
  glfwOSPRayWindow->mainLoop();
  // cleanup remaining objects
  - ospRelease(world);
  - ospRelease(renderer);
  ospRelease(pixelOpData);
  for (auto &op : pixelPipeline)
  