Added Config class and changed constructor

Author: sedonik

app/code/Magento/Newsletter/Model/Config.php

@@ -0,0 +1,47 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\Newsletter\Model;
+
+use Magento\Framework\App\Config\ScopeConfigInterface;
+
+/**
+ * Newsletter configuration model
+ */
+class Config
+{
+    /**
+     * Configuration path to newsletter active setting
+     */
+    const XML_PATH_NEWSLETTER_ACTIVE = 'newsletter/general/active';
+
+    /**
+     * @var ScopeConfigInterface
+     */
+    protected $scopeConfig;
+
+    /**
+     * Config constructor.
+     *
+     * @param ScopeConfigInterface $scopeConfig
+     */
+    public function __construct(
+        ScopeConfigInterface $scopeConfig
+    ) {
+        $this->scopeConfig = $scopeConfig;
+    }
+
+    /**
+     * Returns newsletter's enabled status
+     *
+     * @return bool
+     */
+    public function isActive($scopeType = ScopeConfigInterface::SCOPE_TYPE_DEFAULT)
+    {
+        return $this->scopeConfig->isSetFlag(self::XML_PATH_NEWSLETTER_ACTIVE, $scopeType);
+    }
+}

app/code/Magento/Newsletter/Observer/PredispatchNewsletterObserver.php

@@ -13,6 +13,7 @@
 use Magento\Framework\UrlInterface;
 use Magento\Store\Model\ScopeInterface;
 use Magento\Newsletter\Model\Config;
+use Magento\Framework\App\ObjectManager;
 
 /**
  * Class PredispatchNewsletterObserver
@@ -39,16 +40,16 @@ class PredispatchNewsletterObserver implements ObserverInterface
      *
      * @param ScopeConfigInterface $scopeConfig
      * @param UrlInterface $url
-     * @param Config $config
+     * @param Config|null $config
      */
     public function __construct(
         ScopeConfigInterface $scopeConfig,
         UrlInterface $url,
-        Config $config
+        Config $config = null
     ) {
         $this->scopeConfig = $scopeConfig;
         $this->url = $url;
-        $this->config = $config;
+        $this->config = $config ?: ObjectManager::getInstance()->get(Config::class);
     }
 
     /**