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).
}
    CMutableTransaction txNew;
    FeeCalculation feeCalc;
    CAmount nFeeNeeded;
    int nBytes;
    {
        std::set<CInputCoin> setCoins;
        LOCK(cs_wallet);
        txNew.nLockTime = GetLocktimeForNewTransaction(chain(), GetLastBlockHash(), GetLastBlockHeight());
        {
            std::vector<COutput> vAvailableCoins;
            AvailableCoins(vAvailableCoins, true, &coin_control, 1, MAX_MONEY, MAX_MONEY, 0);
            CoinSelectionParams coin_selection_params; 
            
            
            
            CScript scriptChange;
            
            if (!boost::get<CNoDestination>(&coin_control.destChange)) {
                scriptChange = GetScriptForDestination(coin_control.destChange);
            } else { 
                
                
                
                
                
                
                
                
                CTxDestination dest;