Improve Roadmap and Board components

app/javascript/components/Roadmap/PostList.tsx

@@ -12,14 +12,19 @@ interface Props {
 
 const PostList = ({ posts, boards }: Props) => (
   <div className="postList">
-    {posts.map((post, i) => (
-      <PostListItem
-        title={post.title}
-        boardName={boards.find(board => board.id === post.board_id).name}
+    {
+      posts.length > 0 ?
+        posts.map((post, i) => (
+          <PostListItem
+            title={post.title}
+            boardName={boards.find(board => board.id === post.board_id).name}
 
-        key={i}
-      />
-    ))}
+            key={i}
+          />
+        ))
+      :
+        <span className="infoText text-muted">There are no posts that have this status.</span>
+    }
   </div>
 );