MDL-57967 core_message: do not process conversations from deleted users

message/classes/api.php

@@ -417,7 +417,8 @@ class api {
         $userfields = \user_picture::fields('', array('lastaccess'));
         $userssql = "SELECT $userfields
                      FROM {user}
-                     WHERE id $useridsql";
+                     WHERE id $useridsql
+                       AND deleted = 0";
         $otherusers = $DB->get_records_sql($userssql, $usersparams);
 
         // Similar to the above use case, we need to pull the contact information and again this has
@@ -478,6 +479,11 @@ class api {
                 $conversation->$prop = ($otheruser) ? $otheruser->$prop : null;
             }
 
+            // Do not process a conversation with a deleted user.
+            if (empty($conversation->id)) {
+                continue;
+            }
+
             // Add the contact's information, if we have one.
             $conversation->blocked = ($contact) ? $contact->blocked : null;