quickfix inventory view

main/models.py

@@ -39,8 +39,11 @@ class Product(models.Model):
             if self.inventory_amount <= sum_units:
                 return up['unit_price']
 
+        if len(unit_prices) > 0:
             return unit_prices[0]['unit_price']
 
+        return 0
+
     @property
     def wholesale_value(self):
         return self.wholesale_unit_price * self.inventory_amount