Fixed: enumerate the Seasonrankings starting with 1

Fixed: Logging error when a value changed from/to None

src/mahjong_ranking/managers.py

@@ -184,7 +184,7 @@ class SeasonRankingManager(models.Manager):
         if until or force_recalc:
             for ranking in self.filter(season=season):
                 ranking.recalculate(until=until)
-        for placement, ranking in enumerate(self.season_rankings(season)):
+        for placement, ranking in enumerate(self.season_rankings(season), start=1):
             ranking.placement = placement
             ranking.save(force_update=True, update_fields=['placement'])
 
@@ -249,5 +249,5 @@ class KyuDanRankingManager(models.Manager):
                     LOGGER.warning(
                         "%(user)s recalc shows differences in %(attr)s! old: %(old)d, new: %(new)d",
                         {'user': ranking.user, 'attr': attr,
-                         'old': old_value, 'new': getattr(ranking, attr)}
+                         'old': old_value or 0, 'new': getattr(ranking, attr) or 0}
                     )