head: fix head with no sub

files/templates/home.html

@@ -11,7 +11,7 @@
 
 {% block head_final %}
 {% set preview = sub.siderbarurl if sub and sub.sidebarurl else sub.bannerurl %}
-
+{% if sub %}
 <meta property="og:type" content="article">
 <meta property="og:title" content="/h/{{sub}}">
 <meta property="og:site_name" content="{{SITE}}">
@@ -25,7 +25,7 @@
 <meta name="twitter:creator" content="{{SITE_FULL}}">
 <meta name="twitter:image" content="{{preview}}">
 <meta name="twitter:url" content="{{request.full_path}}">
-
+{% endif %}
 {% if sub.sidebar %}
 	<meta property="og:description" name="description" content="{{sub.sidebar}}">
 	<meta name="twitter:description" content="{{sub.sidebar}}">