We are facing this issue if we restart the jenkins.
Since the jenkins is not working properly anymore, we are not sure where this error comes from. Please see for the detailed view the attached logfile

Similar issues:
May 21, 2015 7:38:14 PM hudson.ExpressionFactory2$JexlExpression evaluate
WARNING: Caught exception evaluating: it.killedBuildUrl in /jenkins/job/DUMMY/job/core-test-tech/. Reason: java.lang.reflect.InvocationTargetException
{{java.lang.reflect.InvocationTargetException
Caused by: java.lang.NullPointerException
at org.terracotta.jenkins.plugins.acceleratedbuildnow.AcceleratedBuildNowBadgeAction.getKilledBuildUrl(AcceleratedBuildNowBadgeAction.java:22)}}

Maybe this is coupled with our different issue JENKINS-28538