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.
const CBlockIndex* blockindex;
            if (request.params[0].isNull()) {
                blockindex = CHECK_NONFATAL(active_chainstate.m_chain.Tip());
            } else {
                const uint256 hash(ParseHashV(request.params[0], "blockhash"));
                blockindex = chainman.m_blockman.LookupBlockIndex(hash);
                if (!blockindex) {
                    throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
                }
            }
            UniValue deploymentinfo(UniValue::VOBJ);
            deploymentinfo.pushKV("hash", blockindex->GetBlockHash().ToString());
            deploymentinfo.pushKV("height", blockindex->nHeight);
            deploymentinfo.pushKV("deployments", DeploymentInfo(blockindex, chainman));
            return deploymentinfo;
        },
    };
}
struct CompareBlocksByHeight
{
    bool operator()(const CBlockIndex* a, const CBlockIndex* b) const
    {
        /* Make sure that unequal blocks with the same height do not compare
           equal. Use the pointers themselves to make a distinction. */
        if (a->nHeight != b->nHeight)
          return (a->nHeight > b->nHeight);
        return a < b;
    }
};
static RPCHelpMan getchaintips()