fix empty decoder
diff --git a/apache/meta/heka.yml b/apache/meta/heka.yml
index 13a6764..7c53c64 100644
--- a/apache/meta/heka.yml
+++ b/apache/meta/heka.yml
@@ -2,6 +2,7 @@
 {%- if server.get('enabled', False) and server.site is defined %}
 
 log_collector:
+{%- if server.site|length > 0 %}
   decoder:
 {%- for site_name, site in server.site.iteritems() %}
 {%- if site.type == 'keystone' %}
@@ -14,6 +15,7 @@
           {{ site.get('log', {}).get('custom', {}).format|default('vhost_combined') }}
 {%- endif %}
 {%- endfor %}
+{%- endif %}
 
   input:
 {%- for site_name, site in server.site.iteritems() %}