message: Remove warning in msvc due to static_cast
diff: @@ -705,11 +705,8 @@ std::string BP3Base::GetBPSubStreamName(const std::string &name,
  bpRoot = bpName.substr(lastPathSeparator);
  }
  - int index = rank;
  - if (m_Aggregator.m_IsActive)
  - {
  - index = m_Aggregator.m_SubStreamIndex;
  - }
  + const size_t index =
  + m_Aggregator.m_IsActive ? m_Aggregator.m_SubStreamIndex : rank;
  const std::string bpRankName(bpName + ".dir" + PathSeparator + bpRoot +
  "." + std::to_string(index));
  