Merge pull request imathis#1629 from yous/patch-layout

Set layout to null to suppress warning

Author: imathis

.themes/classic/source/_includes/custom/category_feed.xml

@@ -1,5 +1,5 @@
 ---
-layout: nil
+layout: null
 ---
 <?xml version="1.0" encoding="utf-8"?>
 <feed xmlns="http://www.w3.org/2005/Atom">