diff --git a/admin/tool/monitor/classes/notification_task.php b/admin/tool/monitor/classes/notification_task.php
index ffb1f4a6b57..150129c6a36 100644
--- a/admin/tool/monitor/classes/notification_task.php
+++ b/admin/tool/monitor/classes/notification_task.php
@@ -45,7 +45,9 @@ class notification_task extends \core\task\adhoc_task {
             $subscriptionids = $data->subscriptionids;
             foreach ($subscriptionids as $id) {
                 if ($message = $this->generate_message($id, $eventobj)) {
+                    mtrace("Sending message to the user with id " . $message->userto->id . " for the subscription with id $id...");
                     message_send($message);
+                    mtrace("Sent.");
                 }
             }
         }
@@ -68,6 +70,10 @@ class notification_task extends \core\task\adhoc_task {
             return false;
         }
         $user = \core_user::get_user($subscription->userid);
+        if (empty($user)) {
+            // User doesn't exist. Should never happen, nothing to do return.
+            return false;
+        }
         $context = \context_user::instance($user->id, IGNORE_MISSING);
         if ($context === false) {
             // User context doesn't exist. Should never happen, nothing to do return.
diff --git a/admin/tool/monitor/tests/eventobservers_test.php b/admin/tool/monitor/tests/eventobservers_test.php
index 26d40868f5d..4e601835ec5 100644
--- a/admin/tool/monitor/tests/eventobservers_test.php
+++ b/admin/tool/monitor/tests/eventobservers_test.php
@@ -270,10 +270,12 @@ class tool_monitor_eventobservers_testcase extends advanced_testcase {
      * Run adhoc tasks.
      */
     protected function run_adhock_tasks() {
+        ob_start();
         while ($task = \core\task\manager::get_next_adhoc_task(time())) {
             $task->execute();
             \core\task\manager::adhoc_task_complete($task);
         }
+        ob_clean(); // Suppress mtrace debugging info.
     }
 
     /**