fixed request listener for sub requests

Hotfix for esi subrequests. The subrequests changed the language of the page, so that the language changed in the middle.

Don't forget to also merge into develop.

__Tasks:__

- [ ] test coverage
- [ ] gather feedback for my changes
- [ ] submit changes to the documentation

__Informations:__

| Q             | A
| ------------- | ---
| Tests pass?   | yes
| Fixed tickets | fixes #617 
| BC Breaks     | Subrequests aren't analyzed
| Doc           | none