We started seeing this issue at times, in particular it seems, when two sets of upstream jobs are flagged as being upstream triggers (Why that is happening is another issue).

C:\Jenkins\workspace\Trunk_Dev_D_Done>exit 0
FATAL: null
java.lang.NullPointerException
at hudson.plugins.copyartifact.TriggeredBuildSelector.getBuild(TriggeredBuildSelector.java:61)
at hudson.plugins.copyartifact.TriggeredBuildSelector.getBuild(TriggeredBuildSelector.java:73)
at hudson.plugins.copyartifact.TriggeredBuildSelector.getBuild(TriggeredBuildSelector.java:73)
at hudson.plugins.copyartifact.CopyArtifact.perform(CopyArtifact.java:195)
at hudson.tasks.BuildStepMonitor$1.perform(BuildStepMonitor.java:19)
at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:802)
at hudson.model.Build$BuildExecution.build(Build.java:199)
at hudson.model.Build$BuildExecution.doRun(Build.java:160)
at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:584)
at hudson.model.Run.execute(Run.java:1575)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:46)
at hudson.model.ResourceController.execute(ResourceController.java:88)
at hudson.model.Executor.run(Executor.java:237)