Ensure filter_adminparam is consistently passed

- Updated the `index` action within `Paginable UsersController` to include `filter_admin` in the `query_params` for `paginable_renderise`.
- This addresses the issue where `filter_admin` was sometimes `nil` within the controller, even when it was set to '1' in the browser (#941).

app/controllers/paginable/users_controller.rb

@@ -25,7 +25,7 @@ def index
       paginable_renderise(
         partial: 'index',
         scope: scope,
-        query_params: { sort_field: 'users.surname', sort_direction: :asc },
+        query_params: { sort_field: 'users.surname', sort_direction: :asc, filter_admin: params[:filter_admin] },
         format: :json,
         view_all: !current_user.can_super_admin?
       )