message: Check that the second output of a merge node is a scalar.
diff: @@ -693,6 +693,10 @@ Status GraphProperties::UpdateMergeNode(SymbolicShapeRefiner* shape_refiner,
  InferenceContext* c = shape_refiner->GetContext(node);
  CHECK_NE(c, nullptr);
  + ShapeHandle out1;
  + TF_RETURN_IF_ERROR(c->WithRank(c->output(1), 0, &out1));
  + c->set_output(1, out1);
  +
  ShapeHandle out;
  bool out_initialized = false;
  for (const Edge* e : node->in_edges()) {
  @@ -727,7 +731,6 @@ Status GraphProperties::UpdateMergeNode(SymbolicShapeRefiner* shape_refiner,
  if (!shape_refiner->EquivalentShapes(out, c->output(0))) {
  c->set_output(0, out);
  - c->set_output(1, c->Scalar());
  new_shapes->push(node);
  }
  