check if current track exists before attempting to find associated voicetrack

Author: brookgagnon

obplayer/scheduler/scheduler.py

@@ -64,6 +64,11 @@ def current_voicetrack(self, current_track_position):
             return None
 
         current = self.current()
+
+        # voicetrack is always played relative to the current or next track
+        if not current:
+            return None
+
         track_ends_in = current["duration"] - current_track_position
 
         for voicetrack in self.voicetracks: