the command "bitcoin-cli getblockstats 0000000000000000000c61ff8f761ce509fc8901d3c22d61fec89637042ea2ba" does not work.

It displays "error: Error parsing JSON:0000000000000000000c61ff8f761ce509fc8901d3c22d61fec89637042ea2ba"

but it should display the block stats like the documentation says.

also bitcoin-cli getblockstats 0 does not work. block number must be at least 1 to work. But blocks start at 0.

tested with 0.20.1 on freebsd, another user on IRC acknowledged the problem.
if (has_signal) {
        UniValue statsUV(UniValue::VOBJ);
        std::vector<bool> signals;
        BIP9Stats statsStruct = chainman.m_versionbitscache.Statistics(blockindex, chainman.GetConsensus(), id, &signals);
        statsUV.pushKV("period", statsStruct.period);
        statsUV.pushKV("elapsed", statsStruct.elapsed);
        statsUV.pushKV("count", statsStruct.count);
        if (ThresholdState::LOCKED_IN != current_state) {
            statsUV.pushKV("threshold", statsStruct.threshold);
            statsUV.pushKV("possible", statsStruct.possible);
        }
        bip9.pushKV("statistics", statsUV);
        std::string sig;
        sig.reserve(signals.size());
        for (const bool s : signals) {
            sig.push_back(s ? '#' : '-');
        }
        bip9.pushKV("signalling", sig);
    }
    UniValue rv(UniValue::VOBJ);
    rv.pushKV("type", "bip9");
    if (ThresholdState::ACTIVE == next_state) {
        rv.pushKV("height", chainman.m_versionbitscache.StateSinceHeight(blockindex, chainman.GetConsensus(), id));
    }
    rv.pushKV("active", ThresholdState::ACTIVE == next_state);
    rv.pushKV("bip9", bip9);
    softforks.pushKV(DeploymentName(id), rv);
}
RPCHelpMan getblockchaininfo()