Prevents music overlap

Makes sure to actually stop songs played for players outside the global cycle when changing to the next track in a playlist.

src/main/java/net/knarcraft/minstrel/music/Playlist.java

@@ -126,6 +126,14 @@ public class Playlist {
             }
         }
 
+        //Prevent overlapping music if a song has been played outside the global cycle
+        for (Player player : playerCurrentSong.keySet()) {
+            Song currentSong = playerCurrentSong.get(player);
+            if (currentSong != null) {
+                currentSong.stop(player);
+            }
+        }
+
         Song currentSong = this.songs.get(this.currentlyPlaying);
         currentSong.play(trait, trait.getVolume(), trait.getPitch());
         currentlyPlaying++;