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(pindex) {
        LOCK(cs_blockchange);
        latestblock.hash = pindex->GetBlockHash();
        latestblock.height = pindex->nHeight;
    }
    cond_blockchange.notify_all();
}
static RPCHelpMan waitfornewblock()
{
    return RPCHelpMan{"waitfornewblock",
                "\nWaits for a specific new block and returns useful info about it.\n"
                "\nReturns the current block on timeout or exit.\n",
                {
                    {"timeout", RPCArg::Type::NUM, RPCArg::Default{0}, "Time in milliseconds to wait for a response. 0 indicates no timeout."},
                },
                RPCResult{
                    RPCResult::Type::OBJ, "", "",
                    {
                        {RPCResult::Type::STR_HEX, "hash", "The blockhash"},
                        {RPCResult::Type::NUM, "height", "Block height"},
                    }},
                RPCExamples{
                    HelpExampleCli("waitfornewblock", "1000")
            + HelpExampleRpc("waitfornewblock", "1000")
                },
        [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
{
    int timeout = 0;
    if (!request.params[0].isNull())