Fix username not shown in article comment

views/article.ejs

@@ -27,7 +27,7 @@
           <img src="<%= syzoj.utils.gravatar(comment.user.email, 120) %>">
         </a>
         <div class="content">
-          <a class="author" href="<%= syzoj.utils.makeUrl(['user', comment.user_id]) %>"><%= comment.user.nickname %></a>
+          <a class="author" href="<%= syzoj.utils.makeUrl(['user', comment.user_id]) %>"><%= comment.user.username %></a>
           <div class="metadata">
             <span class="date"><%= syzoj.utils.formatDate(comment.public_time) %></span>
           </div>