`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.
pwallet->BlockUntilSyncedToCurrentChain();
    LockAnnotation lock(::cs_main); 
    auto locked_chain = pwallet->chain().lock();
    LOCK(pwallet->cs_wallet);
    
    int nMinDepth = 1;
    if (!request.params[1].isNull())
        nMinDepth = request.params[1].get_int();
    
    std::string label = LabelFromValue(request.params[0]);
    std::set<CTxDestination> setAddress = pwallet->GetLabelAddresses(label);
    
    CAmount nAmount = 0;
    for (const std::pair<const uint256, CWalletTx>& pairWtx : pwallet->mapWallet) {
        const CWalletTx& wtx = pairWtx.second;
        if (wtx.IsCoinBase() || !CheckFinalTx(*wtx.tx))
            continue;
        for (const CTxOut& txout : wtx.tx->vout)
        {
            CTxDestination address;
            if (ExtractDestination(txout.scriptPubKey, address) && IsMine(*pwallet, address) && setAddress.count(address)) {
                if (wtx.GetDepthInMainChain(*locked_chain) >= nMinDepth)
                    nAmount += txout.nValue;
            }
        }
    }
    return ValueFromAmount(nAmount);
}
static UniValue getbalance(const JSONRPCRequest& request)