Fix style and add comment about null player

app/src/main/java/org/schabi/newpipe/player/PlayerService.java

@@ -319,13 +319,10 @@ public final class PlayerService extends MediaBrowserServiceCompat {
     public void setPlayerListener(@Nullable final Consumer<Player> listener) {
         this.onPlayerStartedOrStopped = listener;
         if (listener != null) {
-            if (player == null) {
-                listener.accept(null);
-            } else {
+            // if there is no player, then `null` will be sent here, to ensure the state is synced
             listener.accept(player);
         }
     }
-    }
     //endregion
 
     //region Media browser