title: Getting error in Activeadmin NoMethodError - undefined method `login'
body: <p>I am using active admin for admin side.</p>
  
  <p>I installed active-admin gem and executed <code>rails g active_admin:install</code>.</p>
  
  <p>After that when I tried to open login page for admin. I am getting this error.</p>
  
  <blockquote>
    <p>NoMethodError - undefined method `login' for #:</p>
  </blockquote>