`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::string coinbaseAddress = coinbaseKey.GetPubKey().GetID().ToString();
    
    
    std::map<CTxDestination, std::vector<COutput>> list;
    {
        LOCK2(cs_main, wallet->cs_wallet);
        list = wallet->ListCoins(*m_locked_chain);
    }
    BOOST_CHECK_EQUAL(list.size(), 1U);
    BOOST_CHECK_EQUAL(boost::get<CKeyID>(list.begin()->first).ToString(), coinbaseAddress);
    BOOST_CHECK_EQUAL(list.begin()->second.size(), 1U);
    
    BOOST_CHECK_EQUAL(50 * COIN, wallet->GetAvailableBalance());
    
    
    
    
    AddTx(CRecipient{GetScriptForRawPubKey({}), 1 * COIN, false });
    {
        LOCK2(cs_main, wallet->cs_wallet);
        list = wallet->ListCoins(*m_locked_chain);
    }
    BOOST_CHECK_EQUAL(list.size(), 1U);
    BOOST_CHECK_EQUAL(boost::get<CKeyID>(list.begin()->first).ToString(), coinbaseAddress);
    BOOST_CHECK_EQUAL(list.begin()->second.size(), 2U);