message: Don't check for zerocoin spends on a null vin
diff: @@ -256,7 +256,7 @@ public:
  bool IsZerocoinSpend() const
  {
  - return (vin[0].prevout.IsNull() && vin[0].scriptSig[0] == OP_ZEROCOINSPEND);
  + return (vin.size() > 0 && vin[0].prevout.IsNull() && vin[0].scriptSig[0] == OP_ZEROCOINSPEND);
  }
  bool IsZerocoinMint() const
  