`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.
#include <wallet/feebumper.h>
#include <wallet/rpcwallet.h>
#include <wallet/wallet.h>
#include <wallet/walletdb.h>
#include <wallet/walletutil.h>
#include <stdint.h>
#include <univalue.h>
#include <functional>
static const std::string WALLET_ENDPOINT_BASE = "/wallet/";
bool GetWalletNameFromJSONRPCRequest(const JSONRPCRequest& request, std::string& wallet_name)
{
    if (request.URI.substr(0, WALLET_ENDPOINT_BASE.size()) == WALLET_ENDPOINT_BASE) {
        
        wallet_name = urlDecode(request.URI.substr(WALLET_ENDPOINT_BASE.size()));
        return true;
    }
    return false;
}
std::shared_ptr<CWallet> GetWalletForJSONRPCRequest(const JSONRPCRequest& request)
{
    std::string wallet_name;
    if (GetWalletNameFromJSONRPCRequest(request, wallet_name)) {
        std::shared_ptr<CWallet> pwallet = GetWallet(wallet_name);
        if (!pwallet) throw JSONRPCError(RPC_WALLET_NOT_FOUND, "Requested wallet does not exist or is not loaded");
        return pwallet;
    }
    std::vector<std::shared_ptr<CWallet>> wallets = GetWallets();
    return wallets.size() == 1 || (request.fHelp && wallets.size() > 0) ? wallets[0] : nullptr;
}
std::string HelpRequiringPassphrase(CWallet * const pwallet)