[Bug]: Filtering Leave Types by "Created By" crashes with a server error

Description:

On the Time Off module's Configuration page, the Leave Types list has a filter that lets you narrow the list down by who created each leave type. Using this "Created By" filter is supposed to show only the leave types created by the selected user, but instead it crashes the page with a server error.

Steps to Reproduce:

1. Go to Time Off → Configuration → Leave Types.
2. Open the filters panel above the leave types table.
3. Select a value in the "Created By" filter.

Actual Behaviour:

The page immediately breaks and shows an "Internal Server Error" screen with the message: LogicException: The relationship [creator_id] does not exist on the model [Webkul\TimeOff\Models\LeaveType]. The Leave Types list becomes unusable until the page is reloaded.

Expected Behaviour:

Selecting a user in the "Created By" filter should simply filter the Leave Types list to show only the leave types created by that user, with no error.

Screenshot: