Sign out error

gistfile1.rb

<h1>Welcome to Freshitoff</h1>
<p>A simple application for createing To-Do lists.</p>

<div class="btn-group-vertical">
<% @todos.each do |todo| %>
  <button type="button" class="btn btn-default"><%= todo.description %></button>
<% end %>
</div>

<ul class="nav nav-pills">

  <li><a href="#"><%= link_to("Create a new todo", new_todo_path) if current_user %></a></li>

  <li><a href="#"><%= link_to("Sign out", destroy_user_session_path, method: :delete) if current_user %></a></li>
</ul>