When creating a course and/or activating matrix as a communication provider, the room is created properly. Also, when another room name is set.

But if anytime later the room name is changed again and the room name input is left empty, nothing happens. The room name always stays on the value set before.

Steps to reproduce:

1. activate communication provider (with or without a different room name) -> the matrix room is correctly created
2. open the communication provider settings and then delete the room name set there, then save
3. open the communication provider settings again -> the room name is still at the old value (not the course name)

This contradicts the text on the page where it says, that empty input will choose course name.

Proposed solution:

• either set the course name when the input is empty
• or update the description to sth like "course names can only be changed manually after first room creation".

Also this is looely connected to the problem that course names are not synched after creation (MDL-83145).