`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.
if (IsDust(newTxOut, discard_rate) || bnb_used)
                    {
                        nChangePosInOut = -1;
                        nFeeRet += nChange;
                    }
                    else
                    {
                        if (nChangePosInOut == -1)
                        {
                            
                            nChangePosInOut = GetRandInt(txNew.vout.size()+1);
                        }
                        else if ((unsigned int)nChangePosInOut > txNew.vout.size())
                        {
                            strFailReason = _("Change index out of range");
                            return false;
                        }
                        std::vector<CTxOut>::iterator position = txNew.vout.begin()+nChangePosInOut;
                        txNew.vout.insert(position, newTxOut);
                    }
                } else {
                    nChangePosInOut = -1;
                }
                
                
                for (const auto& coin : setCoins) {
                    txNew.vin.push_back(CTxIn(coin.outpoint,CScript()));
                }