Slider URL bugs

[Alkarex]

1. http://localhost:8080/i/?c=subscription&a=feed&id=236 is the URL used after adding a feed. This shows a standalone feed configuration. This configuration cannot be reach through a menu item. It takes the whole width of the panel (no slider).
2. http://localhost:8080/i/?c=subscription&id=236 was the URL used after adding a feed. This URL is not working anymore. The id part of the URL has no effect. The slider does not appear.

Item #1 was introduced by #4631. At the moment, I cannot find where the problem is with item #2. I think if we fix what is the root cause of item #2, we could revert #4631.

Originally posted by @aledeg in https://github.com/FreshRSS/FreshRSS/issues/4727#issuecomment-1280747329

[Alkarex]

@math-GH Could you please check whether this is still relevant?

[math-GH]

#1 is still relevant

(I need to check and understand #2)

[Alkarex]

The other question is whether this is an (important) regression since 1.23.1 or whether it can wait.

[math-GH]

For me it is fine to fix it later.

IMHO it is okay to have the "full page slider" after adding a new feed. I would not expect here a slider