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.

__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