warning: Invalid argument supplied for foreach() in /includes/form.inc on line 573

when submitting a node/add form with inline registration enabled I have this validation warning

warning: Invalid argument supplied for foreach() in /includes/form.inc on line 573

My fix is adding these 2 row at inline_registration.module:37

      // We have no validation function here
      $form['register']['form']['#validate'] = NULL ; 

Hope this help