Fix exception raised if something is added to the queue while Chords isn't present.

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;
     }

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

@@ -51,7 +51,7 @@ public class QueueManager extends QueueThing<Track, Track>
 //        if (inputQueue.size() < QUEUE_TARGET_SIZE)
 //            demandInput(QUEUE_TARGET_SIZE - inputQueue.size());
 
-        if (!handler.isPlaying() || handler.getCurrentTrack() == null)
+        if (handler != null && !handler.isPlaying() || handler.getCurrentTrack() == null)
             handler.requestTrack();
     }