The latest version of JIRA has changed the response codes used for REST resources used by the pie chart and this exposes a bug in atlassian-gadgets in handling responses without a body:

https://studio.atlassian.com/browse/AG-1273

This will break use of these gadgets in Confluence 3.1 and 3.2 as well as on trunk.

JIRA development issue:

http://jdog.atlassian.com/browse/JRADEV-1903