Fix UniqueID deprecation warning

.UniqueID is deprecated and will be removed in a future release. Use .File.UniqueID.

layouts/partials/sidebar.html

@@ -3,9 +3,9 @@
   <h4>{{ .Section | humanize }}</h4>
   <ul>
     {{ range (where .Site.RegularPages "Section" .Section) sort .Site.RegularPages ".Weight" }}
-    <li class="{{ if eq .UniqueID $currentNode.UniqueID }}active {{ end }}">
+    <li class="{{ if eq .File.UniqueID $currentNode.File.UniqueID }}active {{ end }}">
       <a href="{{ .Permalink }}">{{ .Title }}</a>
     </li>
     {{ end }}
   </ul>
-</div>
+</div>