`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.
reserver.reserve();
        const CBlockIndex* const null_block = nullptr;
        const CBlockIndex* stop_block;
        QCOMPARE(
            wallet->ScanForWalletTransactions(chainActive.Genesis(), nullptr, reserver, stop_block, true ),
            CWallet::ScanResult::SUCCESS);
        QCOMPARE(stop_block, null_block);
    }
    wallet->SetBroadcastTransactions(true);
    
    std::unique_ptr<const PlatformStyle> platformStyle(PlatformStyle::instantiate("other"));
    SendCoinsDialog sendCoinsDialog(platformStyle.get());
    TransactionView transactionView(platformStyle.get());
    auto node = interfaces::MakeNode();
    OptionsModel optionsModel(*node);
    AddWallet(wallet);
    WalletModel walletModel(std::move(node->getWallets().back()), *node, platformStyle.get(), &optionsModel);
    RemoveWallet(wallet);
    sendCoinsDialog.setModel(&walletModel);
    transactionView.setModel(&walletModel);
    
    TransactionTableModel* transactionTableModel = walletModel.getTransactionTableModel();
    QCOMPARE(transactionTableModel->rowCount({}), 105);
    uint256 txid1 = SendCoins(*wallet.get(), sendCoinsDialog, CKeyID(), 5 * COIN, false );
    uint256 txid2 = SendCoins(*wallet.get(), sendCoinsDialog, CKeyID(), 10 * COIN, true );
    QCOMPARE(transactionTableModel->rowCount({}), 107);
    QVERIFY(FindTx(*transactionTableModel, txid1).isValid());
    QVERIFY(FindTx(*transactionTableModel, txid2).isValid());
    
    BumpFee(transactionView, txid1, true , "not BIP 125 replaceable" , false );