message: Fix pointer error
diff: @@ -3410,7 +3410,7 @@ bool SignBlock(std::shared_ptr<CBlock> pblock, CWallet& wallet, const CAmount& n
  pblock->nTime = nTimeBlock;
  pblock->vtx[1] = MakeTransactionRef(std::move(txCoinStake));
  pblock->hashMerkleRoot = BlockMerkleRoot(*pblock);
  - pblock->prevoutStake = txCoinStake.vin[0].prevout;
  + pblock->prevoutStake = pblock->vtx[1]->vin[0].prevout;
  // append a signature to our block and ensure that is LowS
  return key.Sign(pblock->GetHashWithoutSign(), pblock->vchBlockSig) && EnsureLowS(pblock->vchBlockSig);
  