Endpoints provide default media type for 'produces' if there is no return type

[cc-jhr]

Setup information
hikaku version: 1.1.1
specification converter: -
implementation converter: SpringConverter
build tool and version: gradle 5.2.1
test framework: junit 5.4.0

Describe the bug
If you use @RestController annotation and a controller method does not provide a return type, then the resulting endpoint lists the default media type for produces.

Expected behavior
Produces list should be empty.

Code samples:
Can you provide specifications or code snippets?

@RestController
@RequestMapping("/todos")
class TodosController {

    @RequestMapping(method = [POST])
    fun createTodo(@RequestBody todo: Todo) { }
}