fixed NPE I saw in my production system. Root cause is unknown, but the...

fixed NPE I saw in my production system. Root cause is unknown, but the javadoc says getNode can return null indeed, so making the code bit more defensive

java.lang.NullPointerException
	at hudson.model.Queue$JobOffer.canTake(Queue.java:178)
	at hudson.model.Queue$ApplicableJobOfferList.(Queue.java:765)
	at hudson.model.Queue$ApplicableJobOfferList.(Queue.java:757)
	at hudson.model.Queue.pop(Queue.java:682)
	at hudson.model.Executor.grabJob(Executor.java:160)
	at hudson.model.Executor.run(Executor.java:102)



git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@24776 71c3de6d-444a-0410-be80-ed276b4c234a

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

@@ -171,11 +171,14 @@ public class Queue extends ResourceController implements Saveable {
          * Verifies that the {@link Executor} represented by this object is capable of executing the given task.
          */
         public boolean canTake(Task task) {
+            Node node = getNode();
+            if (node==null)     return false;   // this executor is about to die
+
             Label l = task.getAssignedLabel();
-            if(l!=null && !l.contains(getNode()))
+            if(l!=null && !l.contains(node))
                 return false;   // the task needs to be executed on label that this node doesn't have.
 
-            if(l==null && getNode().getMode()== Mode.EXCLUSIVE)
+            if(l==null && node.getMode()== Mode.EXCLUSIVE)
                 return false;   // this node is reserved for tasks that are tied to it
 
             return isAvailable();