Activity chooser does not display if site contains plugins missing from disk

Prerequisites Login as Admin Create a Course Go to the Course Test 1 Force a failure when fetching the activity module data: Physically remove (or move) a module (ex. mod/data) directory from the server (without properly uninstalling) Purge the caches (module directory is sill removed without uninstalling). Restore the module directory back to the mod folder (without purging the cache). Reload the Course page in the browser. Open the activity chooser. confirm that an error notification is displayed within the activity chooser informing that the error prevents adding activities or resources. Test 2 Checkout the branch before the integration of this issue: For master - run the following command git checkout a1087ef6092a70fda62c76018e2b97aae5cf9385 If you hit a screen or message saying that your version of code is older than the current code, then run the following mdk command: mdk run version.php For the 3.9 branch - run the following command git checkout 455e7f50d816c20da96f07b56015ac64df529434 If you hit a screen or message saying that your version of code is older than the current code, then run the following mdk command: mdk run version.php Manually remove the Guest user from the database and purge cache. This includes removing the "siteguest" from the config table. The guest user is the record in the user table with the username "guest". You can run the following query - DELETE FROM mdl_user WHERE username LIKE '%guest%' Reload the Course page in the browser. (do not upgrade the instance) Open the activity chooser. confirm that you see the arrow constantly turning. Test 3 We now need to get our branch back to normal, but don't run through the upgrade just yet. Run the following command (when testing the master branch) git checkout master Run the following command (when testing the 3.9 branch) git checkout MOODLE_39_STABLE Purge the cache, and on the course page open the activity chooser. Confirm that you now see a message that the site guest user is missing. Now run through the upgrade. Check that the guest user has been restored. The guest user is the user in the the user table with the username of 'guest'. confirm a guest user exists in the database in both the config and user table. Reload the Course page in the browser. Open the activity chooser. confirm that there is NOT an error within the activity chooser and the activity chooser is functional.