Show scheduled recordings after version 3 update

[dennis531]

Version
master

Describe the bug
In plugin version 2, recordings can be planned in an empty series. After the update to v3, the same course has no playlists and the "Aufzeichung planen" menu entry is hidden. In that case, the user can not see his scheduled recordings until a playlist is created.

To Reproduce
Steps to reproduce the behavior:

1. Go to course in SOP v2
2. Plan a recording in a course without videos
3. Update to SOP v3
4. Open the same course in the new version
5. "Aufzeichnungen planen" menu entry is hidden, see screenshot

Expected behavior
The plugin should show the "Aufzeichnungen planen" menu entry if no playlist is created, or a playlist should be created in the migrations if at least one scheduled recording is available in the course.

Screenshots