[12.x] Fix type casting for environment variables in config files (#6637)

* Update app.php

* Update cache.php

* Update database.php

* Update logging.php

* Update mail.php

config/database.php

@@ -147,7 +147,7 @@ return [
 
         'options' => [
             'cluster' => env('REDIS_CLUSTER', 'redis'),
-            'prefix' => env('REDIS_PREFIX', Str::slug(env('APP_NAME', 'laravel')).'-database-'),
+            'prefix' => env('REDIS_PREFIX', Str::slug((string) env('APP_NAME', 'laravel')).'-database-'),
             'persistent' => env('REDIS_PERSISTENT', false),
         ],