message: Check whether tx is in chain in ContextualCheckZerocoinMint().
diff: @@ -1245,7 +1245,8 @@ bool ContextualCheckZerocoinMint(const CTransaction& tx, const PublicCoin& coin,
  if (pindex->nHeight >= Params().Zerocoin_Block_V2_Start() && Params().NetworkID() != CBaseChainParams::TESTNET) {
  //See if this coin has already been added to the blockchain
  uint256 txid;
  - if(zerocoinDB->ReadCoinMint(coin.getValue(), txid))
  + int nHeight;
  + if (zerocoinDB->ReadCoinMint(coin.getValue(), txid) && IsTransactionInChain(txid, nHeight))
  return error("%s: pubcoin %s was already accumulated in tx %s", __func__,
  coin.getValue().GetHex().substr(0, 10),
  txid.GetHex());
  