controllers: refactor only param includes.

Add extra includes needed by the `only` param inside `respond_with`.

app/controllers/mod_actions_controller.rb

@@ -2,7 +2,9 @@ class ModActionsController < ApplicationController
   respond_to :html, :xml, :json
 
   def index
-    @mod_actions = ModAction.paginated_search(params).includes(model_includes(params))
+    @mod_actions = ModAction.paginated_search(params)
+    @mod_actions = @mod_actions.includes(:creator) if request.format.html?
+
     respond_with(@mod_actions)
   end
 
@@ -12,14 +14,4 @@ class ModActionsController < ApplicationController
       fmt.html { redirect_to mod_actions_path(search: { id: @mod_action.id }) }
     end
   end
-
-  private
-
-  def default_includes(params)
-    if ["json", "xml"].include?(params[:format])
-      []
-    else
-      [:creator]
-    end
-  end
 end