See https://github.com/xwiki/xwiki-platform/blob/12066f6ae9c13e86fc4b0ce01953d55afe162e86/xwiki-platform-core/xwiki-platform-notifications/xwiki-platform-notifications-filters/xwiki-platform-notifications-filters-default/src/main/java/org/xwiki/notifications/filters/internal/UserAddedEventListener.java#L134-L137 which is missing a check for null. |