message: Fix segfault from failure to unlock
diff: @@ -493,7 +493,7 @@ bool CWallet::UnlockZerocoinWallet()
  {
  CKey keyZerocoinMaster;
  if (!GetZerocoinSeed(keyZerocoinMaster))
  - return error("%s: failed to derive zerocoin master key");
  + return error("%s: failed to derive zerocoin master key", __func__);
  auto seedID = keyZerocoinMaster.GetPubKey().GetID();
  if (seedID != zwalletMain->GetMasterSeedID())
  return error("%s: derived zerocoin key %s does not match expected key %s", __func__, seedID.GetHex(), zwalletMain->GetMasterSeedID().GetHex());
  