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).
{
    if (!IsCrypted())
        return false;
    {
        LOCK(cs_wallet);
        vMasterKey.clear();
    }
    NotifyStatusChanged(this);
    return true;
}
bool CWallet::Unlock(const CKeyingMaterial& vMasterKeyIn, bool accept_no_keys)
{
    {
        LOCK(cs_wallet);
        for (const auto& spk_man_pair : m_spk_managers) {
            if (!spk_man_pair.second->CheckDecryptionKey(vMasterKeyIn, accept_no_keys)) {
                return false;
            }
        }
        vMasterKey = vMasterKeyIn;
    }
    NotifyStatusChanged(this);
    return true;
}
std::set<ScriptPubKeyMan*> CWallet::GetActiveScriptPubKeyMans() const