grab the default value from config if this isnt set to avoid setting …

…this variable to null

app/Listeners/Update/V20/Version207.php

@@ -26,7 +26,7 @@ public function handle(Event $event)
 
         // Update .env file
         Installer::updateEnv([
-            'MAIL_MAILER'       =>  config('mail.default'),
+            'MAIL_MAILER'       =>  env('MAIL_DRIVER', config('mail.default')),
         ]);
     }
 }