title: Getting error of undefined method 'valid_password?' with Authlogic
body: <p>I get suddenly the below error on my server with Authlogic</p>
  
  <pre><code>NoMethodError (undefined method `valid_password?' for #&lt;ProductionHouse:0xb53859cc&gt;):
  
  authlogic (2.1.3) [v] lib/authlogic/session/password.rb:191:in `send'
  
  authlogic (2.1.3) [v] lib/authlogic/session/password.rb:191:in `validate_by_password'
  
  authlogic (2.1.3) [v] lib/authlogic/session/callbacks.rb:72:in `validate'
  
  authlogic (2.1.3) [v] lib/authlogic/session/validation.rb:64:in `valid?'
  
  authlogic (2.1.3) [v] lib/authlogic/session/existence.rb:65:in `save'
  
  app/controllers/user_session_controller.rb:162:in `create'
  
  pdfkit (0.5.1) lib/pdfkit/middleware.rb:16:in `call'
  </code></pre>
  
  <p>Cant get the issue sudden happen? Is there any one knows regarding this then please help?</p>