message: Send a reject message is the dsproof was not found when requested
  The dsproof may have been requested incorrectly or it may
  have already been deleted from the cache.
diff: @@ -299,6 +299,11 @@ void static ProcessGetData(CNode *pfrom, const Consensus::Params &consensusParam
  ssDSP << dsp;
  pfrom->PushMessage(NetMsgType::DSPROOF, ssDSP);
  }
  + else
  + {
  + pfrom->PushMessage(NetMsgType::REJECT, std::string(NetMsgType::DSPROOF), REJECT_INVALID,
  + std::string("dsproof requested was not found"));
  + }
  }
  else
  {
  