jenkinsci/jenkins — pull request #1242 by daniel-beck (2014-05-19 20:35:25+00:00)
Title: [FIXED JENKINS-20031] Useful error message when UC not found

Previously, it was simply an NPE one line further down.

It seems kind of stupid to use a different ID than the ID the UC is registered with in Jenkins for the plugin manager form — maybe specific to UpdateSites Manager plugin —, but that appears to be a separate issue.