`Error: The type of key must be string or number but object` is thrown when decoding a object with null as key about msgpack-javascript

[ZumiKua]

Sorry, my bad, the actual message is something like

{ shop:
   { alchemy: { max_count: 70, exec_count: 0 },
     recover_stamina:
      { null: 1,
        count: 30,
        max_count: 30,
        exec_count: 0,
        recovery: 120,
        cost: 40 } } }

the key here is null, which is not supported as the exception stated.