reverse proxy setup - need to call to the ip in pillar list for each domain

*error

local:
    Data failed to compile:
----------
    Rendering SLS 'prod:nginx.ng.vhosts' failed: Jinja variable 'None' has no attribute 'items'
/var/cache/salt/minion/files/prod/nginx/ng/vhosts_config.sls(82):
---
[...]
    {{ sls_block(nginx.vhosts.dir_opts) }}
    - name: {{ nginx.lookup.vhost_available }}
{%- endif %}

# Manage the actual vhost files
{% for vhost, settings in nginx.vhosts.managed.items() %}    <======================
{% endfor %}

# Managed enabled/disabled state for vhosts
{% for vhost, settings in nginx.vhosts.managed.items() %}
{% if settings.config != None %}
[...]
---

domain_datas.sls

staging_servers:
  domains:
    staging.siteurl.com:
      ip: 192.168.0.100

nginx.ng.pillar.init.sls

include:
  - webserver.reverse_proxy.domain_data

nginx:
  ng:
    package:
      opts:
        fromrepo: {{ salt['grains.get']('oscodename') }}
    lookup:
      vhost_enabled: /var/www/nginx/vhosts
      package: nginx-common
    server:
      config:
        user: www-data
        worker_processes: auto
        pid: /run/nginx.pid
        events:
          worker_connections: 1024
          multi_accept: 'on'
          use: epoll

        http: 
          sendfile: 'on'
          tcp_nopush: 'on'
          keepalive_timeout: 65
          types_hash_max_size: 2048
          include: 
            - /etc/nginx/mime.types
            - /etc/nginx/conf.d/*.conf
            - /var/www/nginx/*.conf
            - /etc/nginx/sites-enabled/*
          default_type:  applications/octet-stream
          access_log: /var/log/nginx/access.log
          error_log: /var/log/nginx/error.log
          gzip: 'on'

    vhosts:
      dir_opts:
        user: www-data
        group: www-data
        dir_mode: 755
      managed_opts:
        user: www-data
        group: www-data 
        mode: 644
      symlink_opts:
        user: www-data
        group: www-data
        mode: 644
      managed:
        {%- set staging_server_data = pillar.get('staging_servers', {} ) %}
        {%- set default_params = dict(ip=empty) %}
        {%- for domain, domain_data in staging_server_data.get('domains', {}).items() %}
          {%- if domain_data is not mapping %}
            {%- set ip = default_params['ip'] %}
          {%- else %}
            {%- set ip = domain_data.get('ip', default_params['ip'] ) %}
          {%- endif %}
        rev-{{ domain }}.conf:
          enabled: True
          config:
            - server:
              - listen:
                - 80
              - listen:
                - '[::]:80'
              - server_name: 
                - {{ domain }}
              - location /:
                - proxy_pass:
                  - http://{{ ip }}:80/
                - proxy_redirect:
                  - off
                - proxy_set_header:
                  - Host $http_host
                - proxy_set_header:
                  - X-Real-IP $remote_addr
                - proxy_set_header:
                  - X-Forwarded-For  $proxy_add_x_forwarded_for
                - proxy_max_temp_file_size:
                  - 0
                - client_max_body_size:
                  - 10m
                - client_body_buffer_size:
                  - 128k
                - proxy_connect_timeout:
                  - 90
                - proxy_send_timeout:
                  - 90
                - proxy_read_timeout:
                  - 90
                - proxy_buffer_size:
                  - 4k
                - proxy_buffers:
                  - 4 32k
                - proxy_busy_buffers_size:
                  - 64k
                - proxy_temp_file_write_size:
                  - 64k
            {%- endfor %}