fix

lib/Providers/DefaultServiceProvider.php

@@ -2,6 +2,7 @@
 
 namespace  Bx\Discount\Providers;
 
+use Bx\Discount\ElementSpider;
 use Wt\Core\Interfaces\IApp;
 use Wt\Core\Providers\ADefaultServiceProvider;
 
@@ -15,5 +16,6 @@ class DefaultServiceProvider extends ADefaultServiceProvider
         $container = $this->app->container();
         $config = $this->app->config();
 
+        $container->singleton(ElementSpider::class);
     }
 }