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 (nDepth == 0 && wtx.mapValue.count("replaced_by_txid")) {
            safeTx = false;
        }
        if (fOnlySafe && !safeTx) {
            continue;
        }
        if (nDepth < min_depth || nDepth > max_depth) {
            continue;
        }
        for (unsigned int i = 0; i < wtx.tx->vout.size(); i++) {
            
            if (coinControl && !coinControl->m_add_inputs && !coinControl->IsSelected(COutPoint(entry.first, i))) {
                continue;
            }
            if (wtx.tx->vout[i].nValue < nMinimumAmount || wtx.tx->vout[i].nValue > nMaximumAmount)
                continue;
            if (coinControl && coinControl->HasSelected() && !coinControl->fAllowOtherInputs && !coinControl->IsSelected(COutPoint(entry.first, i)))
                continue;
            if (IsLockedCoin(entry.first, i))
                continue;
            if (IsSpent(wtxid, i))
                continue;
            isminetype mine = IsMine(wtx.tx->vout[i]);