`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.
{
    if (request.fHelp || request.params.size() != 0)
        throw std::runtime_error(
            "listwallets\n"
            "Returns a list of currently loaded wallets.\n"
            "For full information on the wallet, use \"getwalletinfo\"\n"
            "\nResult:\n"
            "[                         (json array of strings)\n"
            "  \"walletname\"            (string) the wallet name\n"
            "   ...\n"
            "]\n"
            "\nExamples:\n"
            + HelpExampleCli("listwallets", "")
            + HelpExampleRpc("listwallets", "")
        );
    UniValue obj(UniValue::VARR);
    for (const std::shared_ptr<CWallet>& wallet : GetWallets()) {
        if (!EnsureWalletIsAvailable(wallet.get(), request.fHelp)) {
            return NullUniValue;
        }
        LOCK(wallet->cs_wallet);
        obj.push_back(wallet->GetName());
    }
    return obj;
}
static UniValue loadwallet(const JSONRPCRequest& request)