`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 || request.params.size() > 2)
        throw std::runtime_error(
            "getreceivedbyaddress \"address\" ( minconf )\n"
            "\nReturns the total amount received by the given address in transactions with at least minconf confirmations.\n"
            "\nArguments:\n"
            "1. \"address\"         (string, required) The bitcoin address for transactions.\n"
            "2. minconf             (numeric, optional, default=1) Only include transactions confirmed at least this many times.\n"
            "\nResult:\n"
            "amount   (numeric) The total amount in " + CURRENCY_UNIT + " received at this address.\n"
            "\nExamples:\n"
            "\nThe amount from transactions with at least 1 confirmation\n"
            + HelpExampleCli("getreceivedbyaddress", "\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XX\"") +
            "\nThe amount including unconfirmed transactions, zero confirmations\n"
            + HelpExampleCli("getreceivedbyaddress", "\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XX\" 0") +
            "\nThe amount with at least 6 confirmations\n"
            + HelpExampleCli("getreceivedbyaddress", "\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XX\" 6") +
            "\nAs a JSON-RPC call\n"
            + HelpExampleRpc("getreceivedbyaddress", "\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XX\", 6")
       );
    
    
    pwallet->BlockUntilSyncedToCurrentChain();