Laravel: How to through 404 if the user enter the ID manually in the route?

Building an app (Blog/posts). Where only auth users can edit their post(which ofcourse belongs to them only). For example, Post with an id of 15 belongs to particular user, so the if he edits it, the route will be like this

http://localhost:8000/post/15/edit

this is correct.

But when the user enters any other post ID(which doesn't belongs to him) in the route, it shows

http://localhost:8000/post/16/edit

ErrorException (E_NOTICE)
Trying to get property 'user_id' of non-object

How to show unauthorised page in this case?

via Chebli Mohamed