Fix type in FreshRSS_User_Mailer (#6130)

fix https://github.com/FreshRSS/FreshRSS/issues/6129

app/Mailers/UserMailer.php

@@ -11,6 +11,10 @@ class FreshRSS_User_Mailer extends Minz_Mailer {
 	 */
 	protected $view;
 
+	public function __construct() {
+		parent::__construct(FreshRSS_View::class);
+	}
+
 	public function send_email_need_validation(string $username, FreshRSS_UserConfiguration $user_config): bool {
 		Minz_Translate::reset($user_config->language);