message: minor updates to ROErrorDecorator
diff: @@ -29,6 +29,10 @@ void ROErrorDecorator::execute(std::shared_ptr<AcceleratorBuffer> buffer,
  std::string json((std::istreambuf_iterator<char>(t)),
  std::istreambuf_iterator<char>());
  + if (json.empty()) {
  + xacc::error("Invalid ROError JSON file: " + roeStr);
  + }
  +
  Document d;
  d.Parse(json);
  std::map<int, double> piplus, piminus;
  @@ -130,6 +134,9 @@ std::vector<std::shared_ptr<AcceleratorBuffer>> ROErrorDecorator::execute(
  std::ifstream t(roeStr);
  std::string json((std::istreambuf_iterator<char>(t)),
  std::istreambuf_iterator<char>());
  + if (json.empty()) {
  + xacc::error("Invalid ROError JSON file: " + roeStr);
  + }
  Document d;
  d.Parse(json);
  @@ -177,7 +184,6 @@ std::vector<std::shared_ptr<AcceleratorBuffer>> ROErrorDecorator::execute(
  (bitString[buffer->size() - 1 - j] == '1' ? -1 : 1) - piminus[j];
  prod *= (numerator / denom);
  }
  -
  fixedExp += ((double)count / (double)nShots) * prod;
  }
  b->addExtraInfo("ro-fixed-exp-val-z", ExtraInfo(fixedExp));
  