message: [RPC] Return RandomX seed also if no miningaddress is set
  in `getblocktemplate` rpc.
diff: @@ -780,13 +780,13 @@ static UniValue getblocktemplate_impl(const std::string &strMode, const UniValue
  }
  }
  if constexpr (nPoWType == CBlockHeader::RANDOMX_BLOCK) { // if (pblock->IsRandomX()) {
  + result.pushKV("rxrpcseed", GetKeyBlock(pblock->nHeight).GetHex());
  std::string address = gArgs.GetArg("-miningaddress", "");
  if (IsValidDestinationString(address)) {
  static std::string lastheader = "";
  if (mapRandomXTemplates.count(lastheader)) {
  if (pblock->nTime - 60 < mapRandomXTemplates.at(lastheader).nTime) {
  result.pushKV("rxrpcheader", lastheader);
  - result.pushKV("rxrpcseed", GetKeyBlock(pblock->nHeight).GetHex());
  return result;
  }
  }
  @@ -795,7 +795,6 @@ static UniValue getblocktemplate_impl(const std::string &strMode, const UniValue
  ssBlockHeader << CRandomXInput(*pblock);
  std::string blockHeaderHex = HexStr(ssBlockHeader);
  result.pushKV("rxrpcheader", blockHeaderHex);
  - result.pushKV("rxrpcseed", GetKeyBlock(pblock->nHeight).GetHex());
  mapRandomXTemplates[blockHeaderHex] = *pblock;
  lastheader = blockHeaderHex;
  }
  