message: Avoid crash when picking returns a volumetric model
diff: @@ -133,6 +133,11 @@ OSPPickResult Renderer::pick(
  if (res.hasHit) {
  auto *instance = (*world->instances)[instID];
  auto *group = instance->group.ptr;
  + if (!group->geometricModels)
  + {
  + res.hasHit = false;
  + return res;
  + }
  auto *model = (*group->geometricModels)[geomID];
  instance->refInc();
  