Laravel 5.8 on demand notification error Call to a member function create() on null

When I do this, the user receives email without error: Notification::send($user, new TicketNotification($details));

But, when I do this, the user also receives an email , but with an error in screenshot below Notification::route('mail', $user->email)->notify(new TicketNotification($details));

Error: Call to a member function create() on null

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Do have any idea why ? How can I avoid this error. I

via Chebli Mohamed