Fix Soundcloud comments crash by handling null page URLs

[Ecomont]

Description

This PR fixes the IllegalArgumentException: Page doesn't contain an URL crash when trying to extract comments from SoundCloud tracks that have no comments or have them disabled (e.g., https://soundcloud.com/user-722618400/a-real-playa).

Previously, SoundcloudCommentsExtractor threw an exception if page.getUrl() or next_href was null or empty. This changes the behavior to gracefully return an empty InfoItemsPage or set a null next page, aligning with how the extractor should handle empty datasets without crashing the client app.

Resolves #1243
Helps resolve TeamNewPipe/NewPipe#11728

• I carefully read the contribution guidelines and agree to them.
• I have tested the API against NewPipe.
• I agree to create a pull request for NewPipe as soon as possible to make it compatible with the changed API.

[TobiGr]

Thank you. Please add a test for the URL mentioned above to ensure that we do not introduce a regression at a later point in time.

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[Ecomont]

@TobiGr Thankss I've just pushed the requested tests.

While writing the test for https://soundcloud.com/user-722618400/a-real-playa does have comments on the official website, but still crashes. The problem is that the current SoundcloudCommentsExtractor fails to find the URL/next_href in the json response for this specific track (likely due to an internal API change by SoundCloud for certain tracks).

Because the extactor couldn't find the next_href, it was triggering the IllegalArgumentException at line 44, crashing the entire app

My changes solve two scenarios at once the tracks with genuinely no comments, instead of crashing with IllegalArgumentException("Page doesn't contain an URL"), it now correctly and gracefully returns InfoItemsPage.emptyPage() and tracks like "a-real-playa" where SoundCloud's json fails to provide a valid next_href string, the new isNullOrEmpty(nextHref) ? null : new Page(nextHref) check prevents passing a null string into the Page constructor, which also prevents subsequent crashes when trying to load more items.

Let me know if anything else is needed.

[TobiGr]

Thank you. Some of the new tests are failing.

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[Ecomont]

Thank you. Some of the new tests are failing.

@TobiGr Done