Fix building author pages for authors with no posts

src/templates/author.js

@@ -15,7 +15,7 @@ const Author = props => {
 
   // The `authored_wordpress__POST` returns a simple array instead of an array
   // of edges / nodes. We therefore need to convert the array here.
-  const posts = authored_wordpress__POST.map(post => ({
+  const posts = (totalCount === 0) ? [] : authored_wordpress__POST.map(post => ({
     node: post,
   }))