fix ActiveRecord::Base check

lib/panko/impl/attributes_writer/creator.rb

@@ -7,7 +7,7 @@
 module Panko::Impl
   module AttributesWriter
     def self.create(object)
-      if defined?(ActiveRecord::Base) && object.is_a?(ActiveRecord::Base)
+      if defined?(::ActiveRecord::Base) && object.is_a?(::ActiveRecord::Base)
         return ActiveRecord::Writer.new
       end
 

lib/panko/serialization_descriptor.rb

@@ -152,16 +152,18 @@ def apply_association_filters(associations, only_filters, except_filters)
       end
     end
 
+    EMPTY_OBJECT = {}.freeze
+
     def resolve_filters(options, filter)
-      filters = options.fetch(filter, {})
-      return filters, {} if filters.is_a? Array
+      filters = options.fetch(filter, EMPTY_OBJECT)
+      return filters, EMPTY_OBJECT if filters.is_a? Array
 
       # hash filters looks like this
       # { instance: [:a], foo: [:b] }
       # which mean, for the current instance use `[:a]` as filter
       # and for association named `foo` use `[:b]`
 
-      return [], {} if filters.empty?
+      return [], EMPTY_OBJECT if filters.empty?
 
       attributes_filters = filters.fetch(:instance, [])
       association_filters = filters.except(:instance)