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).
{
    nTime = GetTime();
    vchPubKey = vchPubKeyIn;
    fInternal = internalIn;
    m_pre_split = false;
}
int CWalletTx::GetDepthInMainChain() const
{
    assert(pwallet != nullptr);
    AssertLockHeld(pwallet->cs_wallet);
    if (isUnconfirmed() || isAbandoned()) return 0;
    return (pwallet->GetLastBlockHeight() - m_confirm.block_height + 1) * (isConflicted() ? -1 : 1);
}
int CWalletTx::GetBlocksToMaturity() const
{
    if (!IsCoinBase())
        return 0;
    int chain_depth = GetDepthInMainChain();
    assert(chain_depth >= 0); 
    return std::max(0, (COINBASE_MATURITY+1) - chain_depth);
}
bool CWalletTx::IsImmatureCoinBase() const
{
    
    return GetBlocksToMaturity() > 0;
}
std::vector<OutputGroup> CWallet::GroupOutputs(const std::vector<COutput>& outputs, bool single_coin, const size_t max_ancestors) const {