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.
uint256 filter_header;
    if (!index->LookupFilter(block_index, filter) ||
        !index->LookupFilterHeader(block_index, filter_header)) {
        int err_code;
        std::string errmsg = "Filter not found.";
        if (!block_was_connected) {
            err_code = RPC_INVALID_ADDRESS_OR_KEY;
            errmsg += " Block was not connected to active chain.";
        } else if (!index_ready) {
            err_code = RPC_MISC_ERROR;
            errmsg += " Block filters are still in the process of being indexed.";
        } else {
            err_code = RPC_INTERNAL_ERROR;
            errmsg += " This error is unexpected and indicates index corruption.";
        }
        throw JSONRPCError(err_code, errmsg);
    }
    UniValue ret(UniValue::VOBJ);
    ret.pushKV("filter", HexStr(filter.GetEncodedFilter()));
    ret.pushKV("header", filter_header.GetHex());
    return ret;
},
    };
}
/**
 * Serialize the UTXO set to a file for loading elsewhere.
 *
 * @see SnapshotMetadata
 */
static RPCHelpMan dumptxoutset()