`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.
uint256 txid;
    if (feebumper::CommitTransaction(pwallet, hash, std::move(mtx), errors, txid) != feebumper::Result::OK) {
        throw JSONRPCError(RPC_WALLET_ERROR, errors[0]);
    }
    UniValue result(UniValue::VOBJ);
    result.pushKV("txid", txid.GetHex());
    result.pushKV("origfee", ValueFromAmount(old_fee));
    result.pushKV("fee", ValueFromAmount(new_fee));
    UniValue result_errors(UniValue::VARR);
    for (const std::string& error : errors) {
        result_errors.push_back(error);
    }
    result.pushKV("errors", result_errors);
    return result;
}
UniValue generate(const JSONRPCRequest& request)
{
    std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
    CWallet* const pwallet = wallet.get();
    if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
        return NullUniValue;
    }
    if (request.fHelp || request.params.size() < 1 || request.params.size() > 2) {
        throw std::runtime_error(
            "generate nblocks ( maxtries )\n"
            "\nMine up to nblocks blocks immediately (before the RPC call returns) to an address in the wallet.\n"
            "\nArguments:\n"
            "1. nblocks      (numeric, required) How many blocks are generated immediately.\n"
            "2. maxtries     (numeric, optional) How many iterations to try (default = 1000000).\n"