the crumbIssuer is only available if you have enabled "Prevent Cross Site Request Forgery exploits" in the Jenkins configuration.
If it is failing as that is not enabled it is a bug in the tool - it should check if it is enabled and not use a crumb if not enabled (ie handle the 404 and continue without a crumb).
as a workaround you can enabled the option - but if you have any other API integrations beware they may start failing!
(generally this option is one you should have on IMHO)
/James