fix: resolve crashes and white screen when playing/loading songs

[ujjawalkaushik1110]

Summary

This PR fixes multiple critical bugs that were causing the application to crash, turn white, or do nothing when trying to play/load songs.

Critical Bugs Fixed:

File	Bug	Fix
converter.ht:48	fullAlbums() returned undefined instead of []	Returns [] now
track.ht:30-31	Null pointer crash in radio() when no playlist found	Added null check
browse.ht:19	Syntax error - missing comma after spTCookie	Added comma
user.ht:25	savedPlaylists() used wrong variable in callback	Fixed to use items
auth.ht:119-125	randomBytesFromMath() had no return statement	Added return
auth.ht:127-134	Duplicate mode parameter in getToken()	Removed duplicate
auth.ht:196	Null pointer when credentials null in refreshCredentials()	Added null check
album.ht	Missing export statement	Added export

Enhancements:

• Comprehensive null safety across all converter functions
• Null checks for all endpoint functions (getTrack, getAlbum, getArtist, etc.)
• Graceful fallbacks - functions now return empty arrays/objects instead of crashing
• Fixed track extraction from playlist/saved items (wrapped in objects with track property)
• Fixed album extraction from saved albums (wrapped with album property)
• Optional chaining for nested property access (external_urls?.spotify)
• Default values for missing fields ("Unknown Track", "Unknown Artist", etc.)
• Improved main plugin initialization with proper auth callback

Files Modified:

• src/converter/converter.ht
• src/segments/auth.ht
• src/segments/browse.ht
• src/segments/track.ht
• src/segments/user.ht
• src/segments/album.ht
• src/segments/artist.ht
• src/segments/playlist.ht
• src/segments/search.ht
• src/plugin.ht

Test plan

• Test playing a song from search results
• Test loading user's saved tracks
• Test loading user's saved playlists
• Test loading user's saved albums
• Test browsing home sections
• Test track radio functionality
• Verify no crashes or white screens occur

Fixes #64

[Copilot]

Pull request overview

This PR targets the crashes/white-screen behavior when playing or loading Spotify content by adding null-safety/fallback handling across endpoints and converters, plus tightening auth/token initialization.

Changes:

• Added null/empty-input guards across multiple endpoint methods (track/album/artist/playlist/user/search/browse) with safer fallbacks instead of throwing.
• Fixed converter and endpoint data-shape issues (e.g., saved tracks/albums/playlists wrappers; fullAlbums() returning [] instead of undefined).
• Improved auth/token wiring so the API access token is refreshed into SpotifyGqlApi on auth state changes.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/converter/converter.ht	Adds null-safe pagination and safer conversions/default values; fixes fullAlbums() empty-case return.
src/segments/auth.ht	Fixes missing return in randomBytesFromMath, removes duplicate mode param, and guards refreshCredentials() when credentials are null.
src/segments/browse.ht	Fixes syntax error and adds empty-result fallback for sections(); exports BrowseEndpoint.
src/segments/track.ht	Adds null checks for getTrack/radio, introduces getTracks, and guards save/unsave inputs.
src/segments/user.ht	Adds fallbacks for me() and paginated saved items; fixes playlist converter callback input; adds guards for library-check methods.
src/segments/playlist.ht	Adds guards/fallbacks, unwraps playlist track items to actual tracks, and makes mutating operations return success booleans.
src/segments/artist.ht	Adds guards/fallbacks and introduces getArtists, plus safer handling for top-tracks/related responses.
src/segments/album.ht	Adds guards/fallbacks, introduces getAlbums, and makes save/unsave return success booleans; exports AlbumEndpoint.
src/segments/search.ht	Adds empty-query/data-null fallbacks for all search endpoints.
src/plugin.ht	Updates plugin initialization to react to auth events and safely set the API access token.

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[Copilot]

Same issue as sections(): spTCookie access uses .elementAt(0) on a filtered cookies list and will throw when credentials/cookies are missing or sp_t isn't present. Add null/empty checks and a safe cookie lookup before calling client.browse.homeSection(...), otherwise this endpoint can still crash when unauthenticated.

[Copilot]

spTCookie is derived via auth.credentials["cookies"].where(...).elementAt(0)["value"], which will throw if the user is logged out (credentials null), cookies missing, or the sp_t cookie isn't present. This can still cause the white-screen/crash path. Consider guarding on auth.credentials/cookies and safely selecting the cookie (e.g., firstWhere(..., orElse: () => null) / first?) and returning an empty paginated response or a clear error when unavailable.