docs: update soundtrack api javadoc by twitch revision

rest-helix/src/main/java/com/github/twitch4j/helix/TwitchHelix.java

@@ -586,7 +586,7 @@ HystrixCommand<CategorySearchList> searchCategories(
      * Gets channel information for users
      *
      * @param authToken Auth Token
-     * @param broadcasterIds IDs of the channels to be retrieved
+     * @param broadcasterIds IDs of the channels to be retrieved (up to 100)
      * @return ChannelInformationList
      */
     @RequestLine("GET /channels?broadcaster_id={broadcaster_id}")
@@ -637,6 +637,8 @@ HystrixCommand<ChannelSearchList> searchChannels(
 
     /**
      * Gets the Soundtrack track that the broadcaster is playing.
+     * <p>
+     * If the broadcaster is not playing a track, the endpoint returns HTTP status code 404 Not Found.
      *
      * @param authToken     App access token or User access token.
      * @param broadcasterId The ID of the broadcaster that’s playing a Soundtrack track.

rest-helix/src/main/java/com/github/twitch4j/helix/domain/SoundtrackArtist.java

@@ -3,17 +3,15 @@
 import lombok.AccessLevel;
 import lombok.Data;
 import lombok.Setter;
-import org.jetbrains.annotations.Nullable;
 
 @Data
 @Setter(AccessLevel.PRIVATE)
 public class SoundtrackArtist {
 
     /**
      * The ID of the Twitch user that created the track.
-     * Is null if a Twitch user didn't create the track.
+     * Is an empty string if a Twitch user didn't create the track.
      */
-    @Nullable
     private String creatorChannelId;
 
     /**

rest-helix/src/main/java/com/github/twitch4j/helix/domain/SoundtrackCurrentTrackWrapper.java

@@ -13,12 +13,11 @@ public class SoundtrackCurrentTrackWrapper {
 
     /**
      * A list that contains the Soundtrack track that the broadcaster is playing.
-     * The list is empty if the broadcaster is not playing a track.
      */
     private List<SoundtrackCurrentTrack> data;
 
     /**
-     * @return the Soundtrack track that the broadcaster is playing or empty if the broadcaster is not playing a track.
+     * @return the Soundtrack track that the broadcaster is playing.
      */
     public Optional<SoundtrackCurrentTrack> getTrack() {
         if (data == null || data.isEmpty())