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)

core/src/main/java/hudson/model/Run.java

@@ -400,9 +400,10 @@ public abstract class Run <JobT extends Job<JobT,RunT>,RunT extends Run<JobT,Run
      * <p>
      * When a build is {@link #isBuilding() in progress}, this method
      * returns an intermediate result.
+     * @return The status of the build, if it has completed or some build step has set a status; may be null if the build is ongoing.
      */
     @Exported
-    public Result getResult() {
+    public @CheckForNull Result getResult() {
         return result;
     }
 

core/src/main/java/hudson/tasks/ArtifactArchiver.java

@@ -135,7 +135,8 @@ public class ArtifactArchiver extends Recorder {
 
             String artifacts = build.getEnvironment(listener).expand(this.artifacts);
             if(ws.copyRecursiveTo(artifacts,excludes,new FilePath(dir))==0) {
-                if(build.getResult().isBetterOrEqualTo(Result.UNSTABLE)) {
+                Result result = build.getResult();
+                if (result != null && result.isBetterOrEqualTo(Result.UNSTABLE)) {
                     // If the build failed, don't complain that there was no matching artifact.
                     // The build probably didn't even get to the point where it produces artifacts. 
                     listenerWarnOrError(listener, Messages.ArtifactArchiver_NoMatchFound(artifacts));