Move logout_method to application helper and add fallback to delete if Devise is no present (need a Config for this).

Author: jvortmann

app/helpers/rails_admin/application_helper.rb

@@ -39,6 +39,11 @@ def logout_path
       end
     end
 
+    def logout_method
+      return Devise.sign_out_via if defined?(Devise)
+      :delete
+    end
+
     def wording_for(label, action = @action, abstract_model = @abstract_model, object = @object)
       model_config = abstract_model.try(:config)
       object = abstract_model && object.is_a?(abstract_model.model) ? object : nil

app/views/layouts/rails_admin/_secondary_navigation.html.haml

@@ -7,6 +7,6 @@
     - if user_link = edit_user_link
       %li= user_link
     - if logout_path.present?
-      %li= link_to content_tag('span', t('admin.misc.log_out'), class: 'label label-important'), logout_path, method: Devise.sign_out_via
+      %li= link_to content_tag('span', t('admin.misc.log_out'), class: 'label label-important'), logout_path, method: logout_method
     - if _current_user.respond_to?(:email) && _current_user.email.present?
       %li= image_tag "#{(request.ssl? ? 'https://secure' : 'http://www')}.gravatar.com/avatar/#{Digest::MD5.hexdigest _current_user.email}?s=30", style: 'padding-top:5px'