`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::vector<CKeyID> vAffected;
                CAffectedKeysVisitor(*this, vAffected).Process(txout.scriptPubKey);
                for (const CKeyID &keyid : vAffected) {
                    std::map<CKeyID, int64_t>::const_iterator mi = m_pool_key_to_index.find(keyid);
                    if (mi != m_pool_key_to_index.end()) {
                        WalletLogPrintf("%s: Detected a used keypool key, mark all keypool key up to this key as used\n", __func__);
                        MarkReserveKeysAsUsed(mi->second);
                        if (!TopUpKeyPool()) {
                            WalletLogPrintf("%s: Topping up keypool failed (locked wallet)\n", __func__);
                        }
                    }
                }
            }
            CWalletTx wtx(this, ptx);
            
            if (pIndex != nullptr)
                wtx.SetMerkleBranch(pIndex, posInBlock);
            return AddToWallet(wtx, false);
        }
    }
    return false;
}
bool CWallet::TransactionCanBeAbandoned(const uint256& hashTx) const
{
    auto locked_chain = chain().lock();
    LOCK(cs_wallet);
    const CWalletTx* wtx = GetWalletTx(hashTx);
    return wtx && !wtx->isAbandoned() && wtx->GetDepthInMainChain(*locked_chain) == 0 && !wtx->InMempool();
}
void CWallet::MarkInputsDirty(const CTransactionRef& tx)