Googling for "struts bug tracker" shows as its first hit http://struts.apache.org/issue-tracking.html
The text on that page says "No issue management system is defined. Please check back at a later date."
Down the left edge of that page is a menu with links to Struts-related activities. The "Issue Tracker (JIRA)" link points to https://issues.apache.org/struts/ which is a 404.
Please update both these links to point to the current bug tracker.