Describe the bug

• Node.js version: irrelevant
• OS & version: irrelevant

When setting the responseType option to json and having an afterResponse hook on the got instance (doesn't matter what it contains) the afterResponse hook throws an Error when the response from the request is null

This is caused due to a check that happens when running the registered afterResponse hooks
https://github.com/sindresorhus/got/blob/b1d61c173a681755ac23afb2f155f08801c1e7e4/source/as-promise/index.ts#LL95C2-L95C2

Although 200 responses should have a body in them there are many instances where this behavior is present, and the current "workaround" is to use .json() and remove the responseType: 'json'.
This behavior persists even with the resolveBodyOnly: true option.

Since the proper way of returning these types of requests is with the status code 204 I tried to create it with the same scenario just changing the status code to204 and it seems like got gets a response but it just hangs at some point. Not sure if it's an issue with fastify or got though.

Actual behavior

1. Have an afterResponse hook
2. Add the responseType: 'json' to the request
3. Call the request to an endpoint that returns null
4. Got throws an error The 'afterResponse' hook returned an invalid value

Expected behavior

1. Have an afterResponse hook
2. Add the responseType: 'json' to the request
3. Call the request to an endpoint that returns null
4. Got returns the response as is with the response.body value of null

Code to reproduce

import gotTest from 'got'
import fastify from 'fastify'

const app = fastify({
  logger: true,
})
await app.register(async (app) => {
  app.get('/null-error', async () => {
    return null
  })
})

await app.listen({port: 8080, host: 'localhost'})
await app.ready()


const got = gotTest.extend({
  hooks: {
    afterResponse: [(response) => {
      return response
    }]
  }
})

try {
  await got.get(`http://localhost:8080/null-error`, {responseType: 'json'})
} catch (error) {
  console.log(error)
  throw error
}

Checklist

• I have read the documentation.
• I have tried my code with the latest version of Node.js and Got.