<% if spree_current_user %>
  <ul class="nav navbar-nav">
    <li class="dropdown user user-menu">
      <a href="#" class="dropdown-toggle" data-toggle="dropdown">
        <i class="glyphicon glyphicon-user"></i>
        <span><%= spree_current_user.email %> <i class="caret"></i></span>
      </a>
      <ul class="dropdown-menu">
        <li class="user-header bg-light-blue">
          <p>
            <%= spree_current_user.email %>
          </p>
        </li>
        <% if spree.respond_to? :root_path %>
          <li class="user-body">
            <div class="col-xs-12 text-center" data-hook="store-frontend-link">
              <%= link_to Spree.t(:back_to_store), spree.root_path, :target => '_blank' %>
            </div>
          </li>
        <% end %>

        <li class="user-footer" id="login-nav">
          <div class="pull-left" data-hook="user-account-link">
            <%= link_to Spree.t(:account), nil, class: "btn btn-default btn-flat" %>
          </div>
          <div class="pull-right" data-hook="user-logout-link">
            <%= link_to Spree.t(:logout), spree.admin_logout_path, method: 'delete', class: "btn btn-default btn-flat" %>
          </div>
        </li>
      </ul>
    </li>
  </ul>
<% end %>

<% if current_user %>
  <ul class="nav navbar-nav">
    <li class="dropdown user user-menu">
      <a href="#" class="dropdown-toggle" data-toggle="dropdown">
        <i class="glyphicon glyphicon-user"></i>
        <span><%= current_user.email %> <i class="caret"></i></span>
      </a>
      <ul class="dropdown-menu">
        <li class="user-header bg-light-blue">
          <p>
            <%= current_user.email %>
          </p>
        </li>
        <% if spree.respond_to? :root_path %>
          <li class="user-body">
            <div class="col-xs-12 text-center" data-hook="store-frontend-link">
              <%= link_to Spree.t(:back_to_store), spree.root_path, :target => '_blank' %>
            </div>
          </li>
        <% end %>

        <li class="user-footer" id="login-nav">
          <div class="pull-left" data-hook="user-account-link">
            <%= link_to Spree.t(:account), nil, class: "btn btn-default btn-flat" %>
          </div>
          <div class="pull-right" data-hook="user-logout-link">
            <%= link_to Spree.t(:logout), spree.admin_logout_path, method: 'delete', class: "btn btn-default btn-flat" %>
          </div>
        </li>
      </ul>
    </li>
  </ul>
<% end %>

Use current_user in login header
Use current_user in login header

authorization_failure action have no spree_current_user helper method
