message: Fix wrong error when trying to spend while mint still in the mempool
diff: @@ -2016,6 +2016,8 @@ CAmount CWallet::SelectSpendCoinsForAmount(
  }
  std::list<CZerocoinEntryV3> CWallet::GetAvailableCoins() const {
  + LOCK2(cs_main, cs_wallet);
  +
  std::list<CZerocoinEntryV3> coins;
  CWalletDB(strWalletFile).ListPubCoinV3(coins);
  @@ -2031,15 +2033,19 @@ std::list<CZerocoinEntryV3> CWallet::GetAvailableCoins() const {
  PublicCoinV3(coin.value, coin.get_denomination())).first;
  if (coinHeight == -1) {
  - throw std::runtime_error("Unable to determine the coin height.\n");
  + // Coin still in the mempool.
  + return true;
  }
  +
  if (coinHeight + (ZC_MINT_CONFIRMATIONS - 1) > chainActive.Height()) {
  // Remove the coin from the candidates list, since it does not have the
  // required number of confirmations.
  return true;
  }
  +
  return false;
  });
  +
  return coins;
  }
  