e3: CanonicalHash to return ok as found-marker

[AskAlexSharov]

to fix:

curl --data '{"method":"debug_traceBlockByNumber","params":["0x13C2924"],"id":1,"jsonrpc":"2.0"}' -H "Content-Type: application/json" -X POST localhost:8549
{"jsonrpc":"2.0","id":1,"result":null,"error":{"code":-32000,"message":"invalid arguments; block with hash 0000000000000000000000000000000000000000000000000000000000000000 not found"}}