[req-change] Made retrieving group id robust

Author: pandafy

openwisp_controller/config/static/config/js/relevant_templates.js

@@ -4,7 +4,7 @@ django.jQuery(function ($) {
     backendFieldSelector = "#id_config-0-backend",
     orgFieldSelector = "#id_organization",
     isDeviceGroup = function () {
-      return window._deviceGroup;
+      return window._deviceGroupId !== undefined;
     },
     templatesFieldName = function () {
       return isDeviceGroup() ? "templates" : "config-0-templates";

openwisp_controller/config/templates/admin/device_group/change_form.html

@@ -12,7 +12,6 @@
         (function ($) {
             $(document).ready( function () {
                 window._relevantTemplateUrl = "{{ relevant_template_url | safe }}";
-                window._deviceGroup = true;
                 window._deviceGroupId = "{{ original.pk }}";
                 window.bindDefaultTemplateLoading();
             })