update rolify

app/controllers/admin/conference_controller.rb

@@ -217,8 +217,8 @@ module Admin
     def get_users(role_name)
       @role_users = {}
       # Initialize @role variable, so that view can show the role description
-      @role = Role.where(name: role_name, resource: @conference)
-      @role.blank? ? @role_users[role_name] = @role : @role_users[role_name] = @role.first.users
+      @role = Role.find_by(name: role_name, resource: @conference) || []
+      @role.blank? ? @role_users[role_name] = [] : (@role_users[role_name] = (User.with_role @role.name, @role.resource).to_a)
 
       @role_users
     end

app/models/role.rb

@@ -1,5 +1,5 @@
 class Role < ActiveRecord::Base
-  has_and_belongs_to_many :users
+  has_and_belongs_to_many :users, join_table: :users_roles
   belongs_to :resource, polymorphic: true
 
   scopify

app/models/user.rb

@@ -29,7 +29,6 @@ class User < ActiveRecord::Base
 
   devise(*devise_modules)
 
-  has_and_belongs_to_many :roles
   has_many :openids
 
   attr_accessor :login