`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.
{
    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() != 0)
        throw std::runtime_error(
            "listaddressgroupings\n"
            "\nLists groups of addresses which have had their common ownership\n"
            "made public by common use as inputs or as the resulting change\n"
            "in past transactions\n"
            "\nResult:\n"
            "[\n"
            "  [\n"
            "    [\n"
            "      \"address\",            (string) The bitcoin address\n"
            "      amount,                 (numeric) The amount in " + CURRENCY_UNIT + "\n"
            "      \"label\"               (string, optional) The label\n"
            "    ]\n"
            "    ,...\n"
            "  ]\n"
            "  ,...\n"
            "]\n"