`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.
{
    CAmount nTotal = 0;
    {
        auto locked_chain = chain().lock();
        LOCK(cs_wallet);
        for (const auto& entry : mapWallet)
        {
            const CWalletTx* pcoin = &entry.second;
            if (pcoin->IsTrusted(*locked_chain) && pcoin->GetDepthInMainChain(*locked_chain) >= min_depth) {
                nTotal += pcoin->GetAvailableCredit(*locked_chain, true, filter);
            }
        }
    }
    return nTotal;
}
CAmount CWallet::GetUnconfirmedBalance() const