[scrobbles] Fix failing tests

vrobbler/apps/scrobbles/mixins.py

@@ -89,7 +89,7 @@ class ScrobblableMixin(TimeStampedModel):
             "[scrobble_for_user] called",
             extra={
                 "id": self.id,
-                "media_type": self.media_obj.__class__,
+                "media_type": self.__class__,
                 "user_id": user_id,
                 "scrobble_data": scrobble_data,
             },