Unable to resolve NULL driver for Mail TransportManager

[Rike-cz]

In October CMS 1.1 branch (Laravel 6) plugin throws this exceptions:

Exception: Unable to resolve NULL driver for [October\Rain\Mail\TransportManager].
Skipping \Illuminate\Support\Facades\Mail.
Exception: Unable to resolve NULL driver for [October\Rain\Mail\TransportManager].
Skipping \Illuminate\Support\Facades\Mail.
A new helper file was written to _ide_helper.php