message: Fix first frame
diff: @@ -96,6 +96,8 @@ ospOffline specific parameters:
  {
  auto renderer = root->child("renderer").nodeAs<sg::Renderer>();
  auto fb = root->child("frameBuffer").nodeAs<sg::FrameBuffer>();
  + // disable use of "navFrameBuffer" for first frame
  + root->child("navFrameBuffer")["size"] = fb->size();
  auto &camera = root->child("camera");
  std::string suffix;
  float variance;
  @@ -110,11 +112,6 @@ ospOffline specific parameters:
  if (optDenoiser)
  fb->child("useDenoiser") = true;
  - // Render one warmup frame then clear accumulation.
  - // XXX: First image has been empty without doing this
  - root->renderFrame();
  - camera.markAsModified();
  -
  do {
  // Clear accum and start fresh
  camera.markAsModified();
  