Bug: Back button from an image page goes to wrong url

[fbunoz]

Describe the bug
After viewving an image page from the diaporama, if we want to return to the source document, we obtain a wrong url.

To Reproduce
Steps to reproduce the behavior:

1. Go to a route or outing page
2. Click on the image to open the diaporama.
3. Click on the eye button to open the image page.
4. Click on the back button of the browser, to return to the route page.
5. See the error in red box : "Request failed with status code 400."
   The error is caused by a wrong url : https://www.camptocamp.org/routes/54140/undefined/

Expected behavior
A right url can be :

• https://www.camptocamp.org/routes/54140
• https://www.camptocamp.org/routes/54140/fr
• https://www.camptocamp.org/routes/54140/fr/vallee-d-ailefroide-paroi-de-la-fissure-la-snoopy

Desktop

• Device: PC
• OS: Windows
• Browser : Firefox 129.0.2, Edge 128.0.27...