`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::list<COutputEntry>& listSent, CAmount& nFee, const isminefilter& filter) const
{
    nFee = 0;
    listReceived.clear();
    listSent.clear();
    
    CAmount nDebit = GetDebit(filter);
    if (nDebit > 0) 
    {
        CAmount nValueOut = tx->GetValueOut();
        nFee = nDebit - nValueOut;
    }
    
    for (unsigned int i = 0; i < tx->vout.size(); ++i)
    {
        const CTxOut& txout = tx->vout[i];
        isminetype fIsMine = pwallet->IsMine(txout);
        
        
        
        if (nDebit > 0)
        {
            
            if (pwallet->IsChange(txout))