Only define publisher repo/mirrors if there are some
diff --git a/aptly/files/aptly-publisher.yaml b/aptly/files/aptly-publisher.yaml
index 8f7c4ee..f1af987 100644
--- a/aptly/files/aptly-publisher.yaml
+++ b/aptly/files/aptly-publisher.yaml
@@ -1,5 +1,5 @@
{%- from "aptly/map.jinja" import server with context %}
-{%- if server.repo is defined %}
+{%- if server.repo|default(False) %}
repo:
{%- for repo_name, repo in server.repo.iteritems() %}
{{ repo_name }}:
@@ -19,7 +19,7 @@
repo: {}
{%- endif %}
-{%- if server.mirror is defined %}
+{%- if server.mirror|default(False) %}
mirror:
{%- for mirror_name, mirror in server.mirror.iteritems() %}
{{ mirror_name }}: