PHP Intelephense --Expected type 'object'. Found 'NULL'-- Fix

$this->db would be highlighted as an error, intelephense has an issue with declaring the var as null in the comment.

application/core/model.php

@@ -7,7 +7,7 @@
 class model
 {
     /**
-     * @var null Database Connection
+     * Set $db to null, so we can use it later in the model.
      */
     public $db = null;