`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() != 1)
        throw std::runtime_error(
            "getaddressesbylabel \"label\"\n"
            "\nReturns the list of addresses assigned the specified label.\n"
            "\nArguments:\n"
            "1. \"label\"  (string, required) The label.\n"
            "\nResult:\n"
            "{ (json object with addresses as keys)\n"
            "  \"address\": { (json object with information about address)\n"
            "    \"purpose\": \"string\" (string)  Purpose of address (\"send\" for sending address, \"receive\" for receiving address)\n"
            "  },...\n"
            "}\n"
            "\nExamples:\n"
            + HelpExampleCli("getaddressesbylabel", "\"tabby\"")
            + HelpExampleRpc("getaddressesbylabel", "\"tabby\"")
        );
    LOCK(pwallet->cs_wallet);