fix(articles): Updated warning message condition (#1944)

It will display warning message only when there is no article present.

Author: tejas002

modules/articles/client/views/admin/list-articles.client.view.html

@@ -20,7 +20,7 @@ <h4 class="list-group-item-heading" data-ng-bind="article.title"></h4>
       <p class="list-group-item-text" data-ng-bind="article.content"></p>
     </a>
   </div>
-  <div class="alert alert-warning text-center" data-ng-if="vm.articles.$resolved && !articles.length">
+  <div class="alert alert-warning text-center" data-ng-if="vm.articles.$resolved && !vm.articles.length">
     No articles yet, why don't you <a data-ui-sref="admin.articles.create">create one</a>?
   </div>
 </section>