bugfix null subject and/or nomarkup cause catalog to fail test

views/mixins/catalogtile.pug

@@ -13,7 +13,7 @@ mixin catalogtile(post, index, overboard=false)
 		data-name=post.name
 		data-tripcode=post.tripcode
 		data-subject=post.subject
-		data-filter=((post.subject+post.nomarkup).toLowerCase() || '')
+		data-filter=((post.subject||'')+(post.nomarkup||'')).toLowerCase()
 		data-date=post.date
 		data-replies=post.replyposts
 		data-bump=post.bumped)