Fix empty array get

It was responsible for

    [CRITICAL] Rendering SLS 'base:salt.minion.cert' failed: Jinja variable 'dict object' has no attribute 'cfg01.mk20-lab-advanced.local'
    [ERROR   ] Data passed to highstate outputter is not a valid highstate return: {'local': ["Rendering SLS 'base:salt.minion.cert' failed: Jinja variable 'dict object' has no attribute 'cfg01.mk20-lab-advanced.local'"]}

salt/minion/cert.sls

     - watch:
       - x509: {{ cert_file }}
 
-{%- for ca_path,ca_cert in salt['mine.get'](cert.host, 'x509.get_pem_entries')[cert.host].iteritems() %}
+{%- for ca_path,ca_cert in salt['mine.get'](cert.host, 'x509.get_pem_entries').get(cert.host, {}).iteritems() %}
 
 {%- if '/etc/pki/ca/'+cert.authority in ca_path %}