Make template variables not required

Author: enricostano

templates/requirements.txt.j2

@@ -1,9 +1,9 @@
 # {{ ansible_managed }}
 
-{% for package in odoo_role_odoo_community_packages %}
+{% for package in odoo_role_odoo_community_packages|default([]) %}
 {{ package }}
 {% endfor %}
 
-{% for package in odoo_role_odoo_project_packages %}
+{% for package in odoo_role_odoo_project_packages|default([]) %}
 {{ package }}
 {% endfor %}