message: Improve the error message when importing a flatbuffer which has empty buffers.
diff: @@ -424,6 +424,10 @@ StatusOr<Operation*> BuildExternalConstOp(const tflite::TensorT& tensor,
  StatusOr<Operation*> BuildConstOp(const tflite::TensorT& tensor,
  const std::vector<uint8_t>& buffer,
  OpBuilder builder, Location loc) {
  + if (buffer.empty()) {
  + return errors::InvalidArgument("Constant's buffer may not be empty");
  + }
  +
  TF_ASSIGN_OR_RETURN(auto type, GetTensorType(tensor, builder,
  /*shapeless_are_scalars=*/true,
  /*is_constant=*/true));
  