add data-page-is-empty to growi-not-found-context

packages/app/src/server/views/layout-growi/not_found.html

@@ -12,6 +12,7 @@
     id="growi-not-found-context"
     data-is-not-found-permalink="{% if isNotFoundPermalink %}{{isNotFoundPermalink|json}}{% endif %}"
     data-page-id="{%if pageId %}{{pageId.toString()}}{% endif %}"
+    data-page-is-empty="{% if isEmpty %}{{ isEmpty }}{% endif %}"
   >
   </div>
   <div class="grw-container-convertible">