tests: fixup tests.

app/controllers/tags_controller.rb

@@ -21,7 +21,8 @@ class TagsController < ApplicationController
       @tags = Tag.names_matches_with_aliases(params[:search][:name_matches])
     end
 
-    respond_with(@tags, root: "tags")
+    # XXX
+    respond_with(@tags.map(&:attributes))
   end
 
   def show

app/models/application_record.rb

@@ -235,6 +235,7 @@ class ApplicationRecord < ActiveRecord::Base
     end
 
     def serializable_hash(options = {})
+      options ||= {}
       options[:only] ||= []
       options[:include] ||= []
       options[:methods] ||= []