Bugfix/Correct sort descending lexicographical

[Kokika]

This PR addresses a bug in my initial descending lexicographical sorting implementation (#2487) where:

🐛 Bug:

Null pointer exception during category sort swich.

Incomplete sorting logic for lexicographical descending sort.

🔧 Fix:

Check for null ptr and initailize for 0.

Sorting applied for category filtering too.

Maintains backward compatibility

✅ Verification:

Validated on my phone with android studio

Confirmed no-breaking changes

[github-actions]

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