fix meta/salt with missing pillar

Change-Id: Id9b69605edb04a3e7316713091b6a612e41d1d06
diff --git a/gerrit/meta/salt.yml b/gerrit/meta/salt.yml
index 259da62..aa3fdd1 100644
--- a/gerrit/meta/salt.yml
+++ b/gerrit/meta/salt.yml
@@ -1,5 +1,5 @@
 minion:
-  {%- if pillar.gerrit.client is defined %}
+  {%- if pillar.get('gerrit', {}).get('client') %}
   gerrit:
     {%- from "gerrit/map.jinja" import client with context %}
     gerrit: