In `JSON#generate` and `JSON#fast_generate`:

- When the given `opts` is a `JSON::State` the variable is set to
  `nil`.
- But it will be never used as the next `if` blocks will not be
  executed.
- `JSON::State#configure` does the conversion to `Hash`, the
  conversions in the `if` block are just duplication.
- `JSON::State.new` does the same thing with `configure` when an
  argument is given.

https://github.com/flori/json/commit/5d9ab87f8e