Bug fixed - If moodle returned None as page content of a lesson, moodle-dl crashed.

Bug Fixes: - When modifying config using the moodle-dl config tools, the config file was not truncate. New Feature: - Added support for notifications via [ntfy](https://n

…he TLS ALPN extension is always activated so that moodle-dl can connect to the moodle instance even if it is behind a reverse proxy.