`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_wallet);
    if (nCreateTime <= 1) {
        
        
        nTimeFirstKey = 1;
    } else if (!nTimeFirstKey || nCreateTime < nTimeFirstKey) {
        nTimeFirstKey = nCreateTime;
    }
}
bool CWallet::AddCScript(const CScript& redeemScript)
{
    if (!CCryptoKeyStore::AddCScript(redeemScript))
        return false;
    return WalletBatch(*database).WriteCScript(Hash160(redeemScript), redeemScript);
}
bool CWallet::LoadCScript(const CScript& redeemScript)
{
    /* A sanity check was added in pull #3843 to avoid adding redeemScripts
     * that never can be redeemed. However, old wallets may still contain
     * these. Do not add them to the wallet and warn. */
    if (redeemScript.size() > MAX_SCRIPT_ELEMENT_SIZE)
    {
        std::string strAddr = EncodeDestination(CScriptID(redeemScript));
        WalletLogPrintf("%s: Warning: This wallet contains a redeemScript of size %i which exceeds maximum size %i thus can never be redeemed. Do not use address %s.\n", __func__, redeemScript.size(), MAX_SCRIPT_ELEMENT_SIZE, strAddr);
        return true;
    }
    return CCryptoKeyStore::AddCScript(redeemScript);
}
bool CWallet::AddWatchOnly(const CScript& dest)