message: GUI: Ask user to unlock wallet before signing psbt
diff: @@ -71,6 +71,9 @@ void PSBTOperationsDialog::signTransaction()
  {
  bool complete;
  size_t n_signed;
  +
  + WalletModel::UnlockContext ctx(m_wallet_model->requestUnlock());
  +
  TransactionError err = m_wallet_model->wallet().fillPSBT(SIGHASH_ALL, true /* sign */, true /* bip32derivs */, &n_signed, m_transaction_data, complete);
  if (err != TransactionError::OK) {
  @@ -81,7 +84,9 @@ void PSBTOperationsDialog::signTransaction()
  updateTransactionDisplay();
  - if (!complete && n_signed < 1) {
  + if (!complete && !ctx.isValid()) {
  + showStatus(tr("Cannot sign inputs while wallet is locked."), StatusLevel::WARN);
  + } else if (!complete && n_signed < 1) {
  showStatus(tr("Could not sign any more inputs."), StatusLevel::WARN);
  } else if (!complete) {
  showStatus(tr("Signed %1 inputs, but more signatures are still required.").arg(n_signed),
  