Fix: Opening a playlist from a user playlist reloads the view twice

[Shadorc]

Pull Request Type

• Bugfix
• Feature Implementation
• Documentation
• Other

Related issue

closes #9517
closes #9513 (side effect)

Description

Early exit from watchers that are triggering redundant calls to getPlaylistInfo (debounced or not).
For the fix to work, the state of the playlist needs to be reset, otherwise everyting break on route change. This has the added benefit of fixing issue #9513 too.

Testing

Valid playlist

1. Open a user playlist
2. Enter a valid playlist URL in the search bar
3. Check that the UI does not reload after the first load and does not cause a flicker

Invalid playlist

1. Open a user playlist
2. Enter an invalid playlist URL in the search bar (e.g. https://www.youtube.com/playlist?list=foobar)
3. Check that the UI does not break and display The playlist currently has no videos.

Desktop

• OS: Bazzite
• OS Version:
• FreeTube version: v0.25.1-beta

[PikachuEXE]

Saw from #9517

Open a playlist
Enter another playlist URL in the search bar (e.g. https://www.youtube.com/playlist?list=foobar), can be valid or invalid
Observe that the UI reloads after the first load and causes a flicker

But is it online playlist or user playlist for 1 & 2? I want to reproduce it first

[Shadorc]

But is it online playlist or user playlist for 1 & 2? I want to reproduce it first

User playlists are playlists specific to FreeTube, available in the Playlists tab, right?
If so, is it possible to open a user playlist from a URL?

I have updated this MR title and the issue title + repro steps to be clearer

It does not happen with two YouTube playlists because the issue comes from a change in the selectedUserPlaylistVideos array (it becomes empty when switching to a YouTube playlist).
If it's possible to switch to a user playlist from another user playlists, then the issue would also happen if the two playlists have a different number of videos.