message: [Qt] Ask for passphrase when minting zPIV with a locked wallet
  Show the AskPassphrase dialog when attempting to mint zPIV with a locked
  wallet instead of returning an error needlessly.
diff: @@ -143,11 +143,16 @@ void PrivacyDialog::on_pushButtonMintzPIV_clicked()
  // Reset message text
  ui->TEMintStatus->setPlainText(tr("Mint Status: Okay"));
  - // Wallet must be unlocked for minting
  - if (pwalletMain->IsLocked()){
  - ui->TEMintStatus->setPlainText(tr("Error: your wallet is locked. Please enter the wallet passphrase first."));
  + // Request unlock if wallet was locked or unlocked for mixing:
  + WalletModel::EncryptionStatus encStatus = walletModel->getEncryptionStatus();
  + if (encStatus == walletModel->Locked) {
  + WalletModel::UnlockContext ctx(walletModel->requestUnlock(true));
  + if (!ctx.isValid()) {
  + // Unlock wallet was cancelled
  + ui->TEMintStatus->setPlainText(tr("Error: Your wallet is locked. Please enter the wallet passphrase first."));
  return;
  }
  + }
  QString sAmount = ui->labelMintAmountValue->text();
  CAmount nAmount = sAmount.toInt() * COIN;
  