Fix crash when starting a song without notes.

Vocaluxe/Lib/Song/CSong.cs

@@ -46,6 +46,11 @@ namespace Vocaluxe.Lib.Song
             get { return _CoverLoaded; }
         }
 
+        public bool NotesLoaded
+        {
+            get { return _NotesLoaded; }
+        }
+
         public bool CoverBigLoaded = false;
         public bool BackgroundLoaded = false;
 

Vocaluxe/Screens/CScreenSing.cs

@@ -937,9 +937,11 @@ namespace Vocaluxe.Screens
             float dt = 4f;
             float rt = dt * 0.8f;
 
-            CSong Song = CGame.GetSong();  
+            CSong Song = CGame.GetSong();
             if (Song == null)
                 return null;
+            else if (!Song.NotesLoaded)
+                return null;
 
             float[] Alpha = new float[Song.Notes.Lines.Length * 2];
             CLines[] lines = new CLines[Song.Notes.Lines.Length];