Fix track skipping not clearing the current track.

src/main/java/moe/nekojimi/chords/MusicHandler.java

@@ -95,7 +95,7 @@ public class MusicHandler implements AudioSendHandler, Closeable, Consumer<Track
             {
                 return false;
             }
-            System.out.println("Playing track " + currentTrack.getLocation().getAbsolutePath());
+//            System.out.println("Playing track " + currentTrack.getLocation().getAbsolutePath());
             arrayErr = false;
             byteCount = 3840;
             TrackPlayer player = new TrackPlayer(currentTrack);
@@ -251,6 +251,7 @@ public class MusicHandler implements AudioSendHandler, Closeable, Consumer<Track
         if (!isPlaying())
             return false;
         playingTracks.clear();
+        currentTrack = null;
         requestTrack();
         return true;
     }