fix: $driver type update ?string $driver

Author: Tinywan

src/Adapter/DatabaseAdapter.php

@@ -33,14 +33,14 @@ class DatabaseAdapter implements Adapter, UpdatableAdapter, BatchAdapter, Filter
     /**
      * @var bool
      */
-    private $filtered = false;
+    private bool $filtered = false;
 
     /**
      * RuleModel model.
      *
      * @var RuleModel
      */
-    protected $model;
+    protected RuleModel $model;
 
     /**
      * the DatabaseAdapter constructor.

src/Model/RuleModel.php

@@ -34,8 +34,8 @@ class RuleModel extends Model implements Arrayable
         'v5'    => 'string'
     ];
 
-    /** @var string $driver */
-    protected string $driver;
+    /** @var string|null $driver */
+    protected ?string  $driver;
 
     /**
      * 架构函数
@@ -61,7 +61,7 @@ public function __construct(array $data = [], ?string $driver = null)
      */
     protected function config(string $key = null, $default = null)
     {
-        $driver = $this->driver ?? config('plugin.casbin.webman-permission.permission.default');
+        $driver = $this->driver ?: config('plugin.casbin.webman-permission.permission.default');
         return config('plugin.casbin.webman-permission.permission.' . $driver . '.' . $key, $default);
     }
 }