[FIXED JENKINS-6128] NPE during run - fingerprint cleanup thread

    A job without a firstBuild is not causing an NPE anymore.

changelog.html

@@ -93,7 +93,10 @@ Upcoming changes</a>
     (<a href="http://issues.jenkins-ci.org/browse/JENKINS-8567">issue 8567</a>)
   <li class=bug>
     Shell Task on Windows Slave Uses Incorrect /bin/sh.
-    <<a href="http://issues.jenkins-ci.org/browse/JENKINS-8449">issue 8449</a>)
+    <a href="http://issues.jenkins-ci.org/browse/JENKINS-8449">issue 8449</a>)
+  <li class=bug>
+    NPE during run - fingerprint cleanup thread.
+    <a href="http://issues.jenkins-ci.org/browse/JENKINS-6128">issue 6128</a>)
   <li class=rfe>
     Added the <tt>--mimeTypes</tt> command line option to define additional MIME type mappings.
   <li class=rfe>

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

@@ -683,7 +683,11 @@ public class Fingerprint implements ModelObject, Saveable {
             if(j==null)
                 continue;
 
-            int oldest = j.getFirstBuild().getNumber();
+            Run firstBuild = j.getFirstBuild();
+            if(firstBuild==null)
+                continue;
+
+            int oldest = firstBuild.getNumber();
             if(!e.getValue().isSmallerThan(oldest))
                 return true;
         }