don't choose a frequency if rarity is supplied

dnd_item/types.py

@@ -455,6 +455,7 @@ class ItemGenerator:
         If a rarity is supplied, ensure we return items of that rarity; in this
         case challenge_rating is ignored.
         """
+        if not rarity:
             if challenge_rating in range(1, 5):
                 frequency = "1-4"
             elif challenge_rating in range(5, 11):
@@ -466,7 +467,6 @@ class ItemGenerator:
             else:
                 frequency = "default"
             self.rarity.set_frequency(frequency)
-
         items = []
         for _ in range(count):
             items.append(self.item_class.from_dict(self.random_properties(rarity=rarity)))