ensure not to show presentation button when page is not exists

lib/views/page.html

@@ -146,8 +146,8 @@
     </li>
     {% if page %}
     <li class="pull-right"><a href="#revision-history" data-toggle="tab"><i class="fa fa-history"></i> History</a></li>
-    {% endif %}
     <li class="pull-right"><a href="?presentation=1" class="toggle-presentation"><i class="fa fa-film"></i> {{ t('Presentation Mode') }}</a></li>
+    {% endif %}
   </ul>
   {% endif %}