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).
} else {
                groups.emplace_back(input_coin, output.nDepth, output.tx->IsFromMe(ISMINE_ALL), ancestors, descendants);
            }
        }
    }
    if (!single_coin) {
        for (auto& it : gmap) {
            auto& group = it.second;
            if (full_groups.count(it.first) > 0) {
                
                group.m_ancestors = max_ancestors - 1;
            }
            groups.push_back(group);
        }
    }
    return groups;
}
bool CWallet::IsCrypted() const
{
    return HasEncryptionKeys();
}
bool CWallet::IsLocked() const
{
    if (!IsCrypted()) {
        return false;
    }
    LOCK(cs_wallet);
    return vMasterKey.empty();
}
bool CWallet::Lock()