Steps to replicate

1. Create a new Moodle instance (master) and do not install it.
2. Checkout to the previous weekly release before MDL-77357 by running: git checkout 84bb5725f8ac68032d70669e7255c557f35c34e4
3. Install the site by running: mdk install.
4. Navigate to site and complete any upgrades.
5. Checkout to the latest master branch.
6. Do the site upgrade.
7. Go to Site administration > Experimental > Experimental settings
8. Enable the communication subsystem. Save the changes
9. Create a course with the Communication service field set to Matrix.
10. Filled the room name and room topic with any value. Make sure that both are not empty. and then click the "Save and display" button
11. You will be redirected to the course page.
12. Click Settings to Edit the course.
13. Right-click on the page and choose View page source
14. Observe the top of the page.

Expected result: There is no error.

Actual result: There is an error: Undefined property: stdClass::$topic

— Original steps to replicate —

Two problems need to be fixed.

To reproduce:

1. Go to Site administration > Experimental > Experimental settings
2. Enable the communication subsystem. Save the changes
3. Create a course with the Communication service field set to Matrix.
4. Filled the room name and room topic with any value. Make sure that both are not empty. and then click the "Save and display" button
5. You will be redirected to the course page.
6. Click Settings to Edit the course.
7. Scrolled to the Communication fieldset
   • Expected
     • The room topic is filled by a value that you have set.
   • Actual
     • The room topic is empty
8. Filled the room topic again. Save the changes
   • Expected
     • The room topic is successfully saved
   • Actual
     • Raising an error: Warning: Undefined property: stdClass::$topic in /communication/provider/matrix/classes/matrix_rooms.php on line 123