Run.getResult may be null, so check for that.

Observed in 1.509.2:
Parsing POMs
Failed to transfer Could not find artifact … in central (http://repo.maven.apache.org/maven2)
Archiving artifacts
ERROR: Processing failed due to a bug in the code. Please report this to jenkinsci-users@googlegroups.com
java.lang.NullPointerException
	at hudson.tasks.ArtifactArchiver.perform(ArtifactArchiver.java:138)
	at org.zeroturnaround.jenkins.LiveRebelDeployBuilder.getArtificatOrMetadata(LiveRebelDeployBuilder.java:194)
	at org.zeroturnaround.jenkins.LiveRebelDeployBuilder.uploadConfiguration(LiveRebelDeployBuilder.java:171)
	at org.zeroturnaround.jenkins.LiveRebelDeployBuilder.perform(LiveRebelDeployBuilder.java:108)
	at hudson.tasks.BuildStepMonitor$1.perform(BuildStepMonitor.java:19)
	at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:812)
	at hudson.maven.MavenModuleSetBuild$MavenModuleSetBuildExecution.build(MavenModuleSetBuild.java:828)
	at hudson.maven.MavenModuleSetBuild$MavenModuleSetBuildExecution.doRun(MavenModuleSetBuild.java:779)
	at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:594)
	at hudson.model.Run.execute(Run.java:1575)
	at hudson.maven.MavenModuleSetBuild.run(MavenModuleSetBuild.java:485)