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.
friend ChainstateManager;
};
/**
 * Provides an interface for creating and interacting with one or two
 * chainstates: an IBD chainstate generated by downloading blocks, and
 * an optional snapshot chainstate loaded from a UTXO snapshot. Managed
 * chainstates can be maintained at different heights simultaneously.
 *
 * This class provides abstractions that allow the retrieval of the current
 * most-work chainstate ("Active") as well as chainstates which may be in
 * background use to validate UTXO snapshots.
 *
 * Definitions:
 *
 * *IBD chainstate*: a chainstate whose current state has been "fully"
 *   validated by the initial block download process.
 *
 * *Snapshot chainstate*: a chainstate populated by loading in an
 *    assumeutxo UTXO snapshot.
 *
 * *Active chainstate*: the chainstate containing the current most-work
 *    chain. Consulted by most parts of the system (net_processing,
 *    wallet) as a reflection of the current chain and UTXO set.
 *    This may either be an IBD chainstate or a snapshot chainstate.
 *
 * *Background IBD chainstate*: an IBD chainstate for which the
 *    IBD process is happening in the background while use of the
 *    active (snapshot) chainstate allows the rest of the system to function.
 */
class ChainstateManager