message: Reject Sigma Double Mint
diff: @@ -355,6 +355,10 @@ bool CheckSigmaMintTransaction(
  if (hasCoin) {
  LogPrintf("CheckSigmaMintTransaction: double mint, tx=%s\n",
  txout.GetHash().ToString());
  + return state.DoS(100,
  + false,
  + PUBCOIN_NOT_VALIDATE,
  + "CheckSigmaTransaction: double mint");
  }
  if (!pubCoin.validate())
  