message: Fix horrendous zwalletMain lock/unlock method call.
diff: @@ -320,7 +320,7 @@ bool CWallet::Lock()
  {
  LOCK(cs_KeyStore);
  vMasterKey.clear();
  - pwalletMain->zwalletMain->Lock();
  + if (zwalletMain) zwalletMain->Lock();
  }
  NotifyStatusChanged(this);
  @@ -368,13 +368,15 @@ bool CWallet::Unlock(const CKeyingMaterial& vMasterKeyIn)
  vMasterKey = vMasterKeyIn;
  fDecryptionThoroughlyChecked = true;
  + if (zwalletMain) {
  uint256 hashSeed;
  - if (CWalletDB(pwalletMain->strWalletFile).ReadCurrentSeedHash(hashSeed)) {
  + if (CWalletDB(strWalletFile).ReadCurrentSeedHash(hashSeed)) {
  uint256 nSeed;
  if (!GetDeterministicSeed(hashSeed, nSeed)) {
  return error("Failed to read zPIV seed from DB. Wallet is probably corrupt.");
  }
  - pwalletMain->zwalletMain->SetMasterSeed(nSeed, false);
  + zwalletMain->SetMasterSeed(nSeed, false);
  + }
  }
  }
  