Fix "Uncaught TypeError: can't access property "querySelector", document.querySelector(...) is null" in editor config page on clicking on Add Group button

fix-error-on-clicking-add-group-in-editor-config-page.patch

diff --git a/js/ckeditor.admin.js b/js/ckeditor.admin.js
index a1a0d1a..0dc97a6 100644
--- a/js/ckeditor.admin.js
+++ b/js/ckeditor.admin.js
@@ -191,7 +191,10 @@
         }
       });
       dialog.showModal();
-      $(document.querySelector('.ckeditor-name-toolbar-group').querySelector('input')).attr('value', $group.attr('data-drupal-ckeditor-toolbar-group-name')).trigger('focus');
+      let group = document.querySelector('.ckeditor-name-toolbar-group');
+      if (group) {
+        $(group.querySelector('input')).attr('value', $group.attr('data-drupal-ckeditor-toolbar-group-name')).trigger('focus');
+      }
     }
   };
   Drupal.behaviors.ckeditorAdminButtonPluginSettings = {