Fix check for next request date in case last_played is NULL.

savepointradio/radio/models.py

@@ -184,7 +184,9 @@ class Song(Disableable, Publishable, Timestampable, models.Model):
         Datetime when a song can be requested again.
         """
         if self._is_song():
+            if self.last_played:
                 return self.last_played + Song.music.wait_total()
+            return timezone.now()
         return None
 
     def _is_requestable(self):