Tag Intersection: issue when second tag doesn't exist

In a tag url, providing a non-existent tag leads to the route-not-found page (“Oops! That page doesn’t exist or is private.”)

In a tag intersection url:

  • Case 1: if the first tag doesn’t exist, you get the route-not-found page (same as above),
  • Case 2: if the first tag exists but the second one doesn’t, you get the equivalent of a tag page with no result (“There are no latest topics”).

Beyond the UX inconsistency, this has the following annoying consequence:

In case 2, if you click “New Topic”, the composer is pre-filled with both the existing tag and the non-existing one. If you are not allowed to create tags and you click “Create Topic”, the topic is created with the existing tag only, the other one being silently ignored.

Suggested fix: having case 2 leading to the route-not-found page.