Fix custom author name in RSS template

feed.xml

@@ -35,7 +35,7 @@ layout: compress
     <id>{{ post_absolute_url }}</id>
     <content src="{{ post_absolute_url }}" />
     <author>
-      <name>{{ site.social.name }}</name>
+      <name>{{ post.author | default: site.social.name }}</name>
     </author>
 
   {% if post.categories %}