Laravel - 在null上调用方法，如果为null则返回false

I have ACL set up with laravel. I have the following helper:

function user($user_id = null)
{
    if (!$user_id) return Auth::user();
    return User::where('id', $user_id)->first();
}

I have this helper function so I don't have to type the long Auth::user().

Here's the problem. I have ACL set up so when I do something like the following in my model and the user is not logged in, I get an error.

if (user()->can('edit-blog')) {
   echo 'you can edit blog!';
}

This is the error if the user is not logged in:

Call to a member function can() on null

Now, I have the following code everywhere in my site. I am using ACL in almost every view and model and controller. I don't want to have to do something like the following just to not get the error.

if (user() && user()->can('edit-blog')) {
    // do stuff
}

How can I return false if there is a "null" error or an exception?

** What I have tried **

I have tried try/catch but it does not do anything:

  try {
    if (!$user_id) return Auth::user();
    return User::where('id', $user_id)->first();
} catch (Exception $ex) {
    return false;
}

Thank you for your support.

You need to check if the user is logged in before calling can

if(Auth::check() && user()->can('edit-post')){
    Return true;
 }else{
    Return false;
 }