avoid intl error on date not defined in PostsItem base component (happen on pending view)

packages/nova-base-components/lib/posts/PostsItem.jsx

@@ -62,7 +62,7 @@ class PostsItem extends Component {
           
           <div className="posts-item-meta">
             {post.user? <div className="posts-item-user"><Telescope.components.UsersAvatar user={post.user} size="small"/><Telescope.components.UsersName user={post.user}/></div> : null}
-            <div className="posts-item-date"><FormattedRelative value={post.postedAt}/></div>
+            <div className="posts-item-date">{post.postedAt ? <FormattedRelative value={post.postedAt}/> : <FormattedMessage id="posts.dateNotDefined"/>}</div>
             <div className="posts-item-comments">
               <Link to={Posts.getPageUrl(post)}>
                 <FormattedMessage id="comments.count" values={{count: post.commentCount}}/>

packages/nova-i18n-en-us/lib/en_US.js

@@ -30,6 +30,7 @@ Telescope.strings.en = {
   "posts.created_message": "Post created.",
   "posts.rate_limit_error": "Please wait {details} seconds before posting again.",
   "posts.postedAt": "Posted at",
+  "posts.dateNotDefined": "Date not defined",
 
   "comments.comments": "Comments",
   "comments.count": "{count, plural, =0 {No comments} one {# comment} other {# comments}}",