Merge branch 'forge' of https://bdgit.educoder.net/Hjqreturn/educoder into forge

public/react/src/forge/Activity/ActivityItem.js

@@ -17,7 +17,7 @@ class ActivityItem extends Component{
           <p className="itemLine mt15">
             <img alt="" src={getImageUrl(`images/${item.user_avatar}`)} className="createImage"/>
             <span className="mr20">{item.user_name}</span>
-            <span className="color-grey-9">创建于<span className="ml2 color-grey-6">{item.created_at}</span></span>
+            { item.created_at && <span className="color-grey-9">创建于<span className="ml2 color-grey-6">{item.created_at}</span></span>}
           </p>
         </div>
       </div>