`ScanForWalletTransactions()` has the following comment about its return value:

```
 * Returns null if scan was successful. Otherwise, if a complete rescan was not
 * possible (due to pruning or corruption), returns pointer to the most recent
 * block that could not be scanned.
```

This is not strictly true. If `abortrescan` is called, then `ScanForWalletTransactions()` will return `nullptr`, even though the scan wasn't successful to the tip.

This in turn causes a minor bug in `importmulti`, where the call doesn't return the correct error and warning about potentially not finding transactions if `abortrescan` was called.

I think the correct fix is for `ScanForWalletTransactions()` to inform the caller that the rescan was aborted.
{
    QVBoxLayout* entries = sendCoinsDialog.findChild<QVBoxLayout*>("entries");
    SendCoinsEntry* entry = qobject_cast<SendCoinsEntry*>(entries->itemAt(0)->widget());
    entry->findChild<QValidatedLineEdit*>("payTo")->setText(QString::fromStdString(EncodeDestination(address)));
    entry->findChild<BitcoinAmountField*>("payAmount")->setValue(amount);
    sendCoinsDialog.findChild<QFrame*>("frameFee")
        ->findChild<QFrame*>("frameFeeSelection")
        ->findChild<QCheckBox*>("optInRBF")
        ->setCheckState(rbf ? Qt::Checked : Qt::Unchecked);
    uint256 txid;
    boost::signals2::scoped_connection c(wallet.NotifyTransactionChanged.connect([&txid](CWallet*, const uint256& hash, ChangeType status) {
        if (status == CT_NEW) txid = hash;
    }));
    ConfirmSend();
    QMetaObject::invokeMethod(&sendCoinsDialog, "on_sendButton_clicked");
    return txid;
}
QModelIndex FindTx(const QAbstractItemModel& model, const uint256& txid)
{
    QString hash = QString::fromStdString(txid.ToString());
    int rows = model.rowCount({});
    for (int row = 0; row < rows; ++row) {
        QModelIndex index = model.index(row, 0, {});
        if (model.data(index, TransactionTableModel::TxHashRole) == hash) {
            return index;
        }
    }
    return {};
}
void BumpFee(TransactionView& view, const uint256& txid, bool expectDisabled, std::string expectError, bool cancel)