message: Move code which delays processing of BatchNormalizationOperator.  Currently it checks whether the buffers exist (criteria for when to delay processing), but after a CHECK(IsConstantParameterArray(...)) which will check fail if they don't exist.
diff: @@ -40,6 +40,13 @@ namespace toco {
  const auto& multiplier_array = model->GetArray(bn_op->inputs[2]);
  const auto& offset_array = model->GetArray(bn_op->inputs[3]);
  + // This graph transformation needs to address constant buffers below, so
  + // we need to exit early if these buffers don't exist yet (i.e. if the params
  + // haven't yet been resolved as constants) and will process it once they have.
  + if (!mean_array.buffer || !multiplier_array.buffer || !offset_array.buffer) {
  + return ::tensorflow::Status::OK();
  + }
  +
  CHECK(IsConstantParameterArray(*model, bn_op->inputs[1]) &&
  IsConstantParameterArray(*model, bn_op->inputs[2]) &&
  IsConstantParameterArray(*model, bn_op->inputs[3]))
  @@ -52,13 +59,6 @@ namespace toco {
  CHECK(multiplier_array.data_type == ArrayDataType::kFloat);
  CHECK(offset_array.data_type == ArrayDataType::kFloat);
  - // This graph transformations will need to address constant buffers below,
  - // so we need to exit early if these buffers don't exist (i.e. if the params
  - // haven't yet been resolved as constants).
  - if (!mean_array.buffer || !multiplier_array.buffer || !offset_array.buffer) {
  - return ::tensorflow::Status::OK();
  - }
  -
  // Create the new Mul, Add operators
  auto* mul_op = new MulOperator;
  auto* add_op = new AddOperator;
  