Fix missing install docker.
diff --git a/docker/host.sls b/docker/host.sls
index 2deaf38..1799e7a 100644
--- a/docker/host.sls
+++ b/docker/host.sls
@@ -31,7 +31,7 @@
   - require:
     - pkg: docker_packages
 
-{% if host.install_docker_py %}
+{% if host.install_docker_py is defined and host.install_docker_py %}
 docker-py-requirements:
   pkg.installed:
     - name: python-pip