Merged in skip-duplicate-check-zerocoin-wallet (pull request dashpay#47)

[FIX] Skip checking for duplicate inputs when adding zerocoin txs to the wallet

Approved-by: Cevap

src/wallet/wallet.cpp

@@ -1232,7 +1232,7 @@ bool CWallet::AddToWalletIfInvolvingMe(const CTransactionRef& ptx, const CBlockI
             for (const CTxIn& txin : tx.vin) {
                 std::pair<TxSpends::const_iterator, TxSpends::const_iterator> range = mapTxSpends.equal_range(txin.prevout);
                 while (range.first != range.second) {
-                    if (range.first->second != tx.GetHash()) {
+                    if (range.first->second != tx.GetHash() && range.first->first.hash != uint256()) {
                         LogPrintf("Transaction %s (in block %s) conflicts with wallet transaction %s (both spend %s:%i)\n", tx.GetHash().ToString(), pIndex->GetBlockHash().ToString(), range.first->second.ToString(), range.first->first.hash.ToString(), range.first->first.n);
                         MarkConflicted(pIndex->GetBlockHash(), range.first->second);
                     }