Handle render.ams with nil serializer or adapter

lib/active_model/serializer/null.rb

@@ -0,0 +1,17 @@
+module ActiveModel
+  class Serializer
+    class Null < Serializer
+      def attributes(*)
+        {}
+      end
+
+      def associations(*)
+        {}
+      end
+
+      def serializable_hash(*)
+        {}
+      end
+    end
+  end
+end