message: there's no need to calculate pow rewards when making pos blocks
diff: @@ -122,7 +122,7 @@ std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock(const CScript& sc
  coinbaseTx.vout.resize(1);
  coinbaseTx.vout[0].scriptPubKey = scriptPubKeyIn;
  - if (pblock->IsProofOfWork()) {
  + if (pwallet == nullptr) {
  pblock->nBits = GetNextTargetRequired(pindexPrev, false, chainparams.GetConsensus());
  coinbaseTx.vout[0].nValue = GetProofOfWorkReward(pblock->nBits);
  }
  