Handling Additional HTTP Errors not handled in Laravel controller

If I have handled specific errors, 404 and 403, in a Laravel application but I also want to handle ALL other types of HTTP errors without overriding the defaults I set in place for 404 and 403. How can I achieve that in Laravel?

I have this piece of code that I am working with:

 public function render($request, Exception $exception)
{
    if ($exception){
        return response()->json([
            'status' => $exception->getStatusCode(),
            'error' => $exception->getMessage()
        ]);
    }
    return parent::render($request, $exception);
}

The code above returns the browser's 500 page for all errors, even for errors that were handled in the controller.

Controller where 403 is thrown:

public function update(ProfileUpdate $profileUpdate, $username)
{
   $admin = Misc::getAdminArray();
   if ($admin)     
    {
        $profileUpdate->session()->flash('updated', 'Profile Updated!');
        return redirect()->route('someRoute');
    }
    else
       abort(403);
}