Set @body_classes to admin layout (#9081)

app/controllers/invites_controller.rb

@@ -6,6 +6,7 @@ class InvitesController < ApplicationController
   layout 'admin'
 
   before_action :authenticate_user!
+  before_action :set_body_classes
 
   def index
     authorize :invite, :create?
@@ -44,4 +45,8 @@ class InvitesController < ApplicationController
   def resource_params
     params.require(:invite).permit(:max_uses, :expires_in, :autofollow)
   end
+
+  def set_body_classes
+    @body_classes = 'admin'
+  end
 end