`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.
{
        fCreditCached = false;
        fAvailableCreditCached = false;
        fImmatureCreditCached = false;
        fWatchDebitCached = false;
        fWatchCreditCached = false;
        fAvailableWatchCreditCached = false;
        fImmatureWatchCreditCached = false;
        fDebitCached = false;
        fChangeCached = false;
    }
    void BindWallet(CWallet *pwalletIn)
    {
        pwallet = pwalletIn;
        MarkDirty();
    }
    
    CAmount GetDebit(const isminefilter& filter) const;
    CAmount GetCredit(interfaces::Chain::Lock& locked_chain, const isminefilter& filter) const;
    CAmount GetImmatureCredit(interfaces::Chain::Lock& locked_chain, bool fUseCache=true) const;
    
    
    
    
    CAmount GetAvailableCredit(interfaces::Chain::Lock& locked_chain, bool fUseCache=true, const isminefilter& filter=ISMINE_SPENDABLE) const NO_THREAD_SAFETY_ANALYSIS;
    CAmount GetImmatureWatchOnlyCredit(interfaces::Chain::Lock& locked_chain, const bool fUseCache=true) const;
    CAmount GetChange() const;
    
    int GetSpendSize(unsigned int out, bool use_max_sig = false) const