Return NO_TRACK for empty liked and search track lists (#183)

Author: marouanesouiri

main/src/main/java/com/sedmelluq/discord/lavaplayer/source/soundcloud/SoundCloudAudioSourceManager.java

@@ -306,6 +306,10 @@ private AudioItem extractTracksFromLikedList(JsonBrowser likedTracks, UserInfo u
             }
         }
 
+        if (tracks.isEmpty()) {
+            return AudioReference.NO_TRACK;
+        }
+
         return new BasicAudioPlaylist("Liked by " + userInfo.name, tracks, null, false);
     }
 
@@ -380,6 +384,10 @@ private AudioItem extractTracksFromSearchResults(String query, JsonBrowser searc
             }
         }
 
+        if (tracks.isEmpty()) {
+            return AudioReference.NO_TRACK;
+        }
+
         return new BasicAudioPlaylist("Search results for: " + query, tracks, null, true);
     }