message: Fix bug for GCC 7.0
diff: @@ -212,7 +212,6 @@ bool ZKPOKFromSigmaCmtPedersenVerifier::verify(ZKCommonInput* input,
  long ZKPOKFromSigmaCmtPedersenVerifier::commit(const vector<byte> & e) {
  auto val = committer->generateCommitValue(e);
  auto id = random->getRandom64();
  - id = abs(id);
  committer->commit(val, id);
  return id;
  };
  