message: [RPC] getzerocoinsupply - add checks for null supply
diff: @@ -228,7 +228,12 @@ static UniValue getzerocoinsupply(const JSONRPCRequest& request)
  pblockindex = chainActive.Tip();
  }
  - int64_t totalSupply = pblockindex->nMoneySupply;
  + int64_t totalSupply = 0;
  + if(pblockindex)
  + totalSupply = pblockindex->nMoneySupply;
  +
  + if(!totalSupply)
  + return NullUniValue;
  UniValue resArr(UniValue::VARR);
  for (auto denom : libzerocoin::zerocoinDenomList) {
  