`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.
{
    AssertLockHeld(cs_main);
    AssertLockHeld(cs_wallet);
    vCoins.clear();
    CAmount nTotal = 0;
    for (const auto& entry : mapWallet)
    {
        const uint256& wtxid = entry.first;
        const CWalletTx* pcoin = &entry.second;
        if (!CheckFinalTx(*pcoin->tx))
            continue;
        if (pcoin->IsImmatureCoinBase(locked_chain))
            continue;
        int nDepth = pcoin->GetDepthInMainChain(locked_chain);
        if (nDepth < 0)
            continue;
        
        
        if (nDepth == 0 && !pcoin->InMempool())
            continue;
        bool safeTx = pcoin->IsTrusted(locked_chain);