fixed is_authenticated check

cps/templates/shelf.html

@@ -2,7 +2,7 @@
 {% block body %}
 <div class="discover">
   <h2>{{title}}</h2>
-  {% if g.user.is_authenticated() %}
+  {% if g.user.is_authenticated %}
     {% if (g.user.role_edit_shelfs() and shelf.is_public ) or not shelf.is_public  %}
       <div data-toggle="modal" data-target="#DeleteShelfDialog" class="btn btn-danger">{{ _('Delete this Shelf') }} </div>
       <a href="{{ url_for('edit_shelf', shelf_id=shelf.id) }}" class="btn btn-primary">{{ _('Edit Shelf name') }} </a>