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.
/**
     * The set of all CBlockIndex entries with either BLOCK_VALID_TRANSACTIONS (for
     * itself and all ancestors) *or* BLOCK_ASSUMED_VALID (if using background
     * chainstates) and as good as our current tip or better. Entries may be failed,
     * though, and pruning nodes may be missing the data for the block.
     */
    std::set<CBlockIndex*, node::CBlockIndexWorkComparator> setBlockIndexCandidates;
    
    CCoinsViewCache& CoinsTip() EXCLUSIVE_LOCKS_REQUIRED(::cs_main)
    {
        AssertLockHeld(::cs_main);
        assert(m_coins_views->m_cacheview);
        return *m_coins_views->m_cacheview.get();
    }
    
    CCoinsViewDB& CoinsDB() EXCLUSIVE_LOCKS_REQUIRED(::cs_main)
    {
        AssertLockHeld(::cs_main);
        return m_coins_views->m_dbview;
    }
    
    CTxMemPool* GetMempool()
    {
        return m_mempool;
    }
    
    
    CCoinsViewErrorCatcher& CoinsErrorCatcher() EXCLUSIVE_LOCKS_REQUIRED(::cs_main)