Review changes

Author: litetex

extractor/src/main/java/org/schabi/newpipe/extractor/stream/StreamInfo.java

@@ -395,7 +395,7 @@ private static StreamInfo extractOptionalData(StreamInfo streamInfo, StreamExtra
     /**
      * Preview frames, e.g. for the storyboard / seekbar thumbnail preview
      */
-    private List<Frameset> previewFrames = new ArrayList<>();
+    private List<Frameset> previewFrames = Collections.emptyList();
 
     /**
      * Get the stream type