I'm sometimes getting an invalid json reply from `getwalletinfo` when rescanning is in progress.

The invalid part is this: `"scanning":{"duration":19,"progress":}}` (no value for `progress`).

I can't reliably reproduce this, but I did manage to run into this 3 times now (once every 10-20 attempts or so).

I'm running v0.20.0 and testing against a regtest instance. This happens while doing a batched `importmulti` of 2000 addresses (none of which have history).
latestNow = nSmartTime;
                    }
                    break;
                }
            }
            nTimeSmart = std::max(latestEntry, std::min(blocktime, latestNow));
        } else {
            WalletLogPrintf("%s: found %s in block %s not in index\n", __func__, wtx.GetHash().ToString(), wtx.m_confirm.hashBlock.ToString());
        }
    }
    return nTimeSmart;
}
bool CWallet::AddDestData(WalletBatch& batch, const CTxDestination &dest, const std::string &key, const std::string &value)
{
    if (boost::get<CNoDestination>(&dest))
        return false;
    m_address_book[dest].destdata.insert(std::make_pair(key, value));
    return batch.WriteDestData(EncodeDestination(dest), key, value);
}
bool CWallet::EraseDestData(WalletBatch& batch, const CTxDestination &dest, const std::string &key)
{
    if (!m_address_book[dest].destdata.erase(key))
        return false;
    return batch.EraseDestData(EncodeDestination(dest), key);
}
void CWallet::LoadDestData(const CTxDestination &dest, const std::string &key, const std::string &value)
{
    m_address_book[dest].destdata.insert(std::make_pair(key, value));
}
bool CWallet::GetDestData(const CTxDestination &dest, const std::string &key, std::string *value) const