message: Fix `CHECK`-failure caused by constant folding code.
  We're losing a `const` qualifier here, but unless we get to use more `StatusOr` objects, this is the best alternative.
diff: @@ -1017,7 +1017,12 @@ bool ConstantFolding::IsFoldableUncached(
  }
  }
  for (const auto& output_prop : output_props) {
  - const PartialTensorShape output_shape(output_prop.shape());
  + PartialTensorShape output_shape;
  + if (!PartialTensorShape::BuildPartialTensorShape(output_prop.shape(),
  + &output_shape)
  + .ok()) {
  + return false;
  + }
  if (output_shape.IsFullyDefined()) {
  const int64 num_bytes =
  output_shape.num_elements() * DataTypeSize(output_prop.dtype());
  