serializable_hash and as_json should take options = nil

per ActiveModel::Serialization#serializable_hash
96bb004fc6/activemodel/lib/active_model/serialization.rb
    def serializable_hash(options = nil)
          options ||= {}

Otherwise, passing in nil to `as_json` or `serializable_hash`
makes things blow up when passing nil into attributes

lib/active_model/serializer/adapter.rb

@@ -16,11 +16,11 @@ module ActiveModel
         @options = options
       end
 
-      def serializable_hash(options = {})
+      def serializable_hash(options = nil)
         raise NotImplementedError, 'This is an abstract method. Should be implemented at the concrete adapter.'
       end
 
-      def as_json(options = {})
+      def as_json(options = nil)
         hash = serializable_hash(options)
         include_meta(hash) unless self.class == FlattenJson
         hash

lib/active_model/serializer/adapter/json.rb

@@ -4,9 +4,10 @@ module ActiveModel
   class Serializer
     class Adapter
       class Json < Adapter
-        def serializable_hash(options = {})
+        def serializable_hash(options = nil)
+          options ||= {}
           if serializer.respond_to?(:each)
-            @result = serializer.map{|s| FlattenJson.new(s).serializable_hash }
+            @result = serializer.map{|s| FlattenJson.new(s).serializable_hash(options) }
           else
             @hash = {}
 

lib/active_model/serializer/adapter/json_api.rb

@@ -15,10 +15,11 @@ module ActiveModel
           end
         end
 
-        def serializable_hash(options = {})
+        def serializable_hash(options = nil)
+          options = {}
           if serializer.respond_to?(:each)
             serializer.each do |s|
-              result = self.class.new(s, @options.merge(fieldset: @fieldset)).serializable_hash
+              result = self.class.new(s, @options.merge(fieldset: @fieldset)).serializable_hash(options)
               @hash[:data] << result[:data]
 
               if result[:included]
@@ -27,7 +28,7 @@ module ActiveModel
               end
             end
           else
-            @hash[:data] = attributes_for_serializer(serializer, @options)
+            @hash[:data] = attributes_for_serializer(serializer, options)
             add_resource_relationships(@hash[:data], serializer)
           end
           @hash

lib/active_model/serializer/adapter/null.rb

@@ -2,7 +2,7 @@ module ActiveModel
   class Serializer
     class Adapter
       class Null < Adapter
-        def serializable_hash(options = {})
+        def serializable_hash(options = nil)
           {}
         end
       end