From 425be8515cfaabd19de5db6a10c3f82875fd72f9 Mon Sep 17 00:00:00 2001
From: Jesse Glick <jglick@cloudbees.com>
Date: Thu, 13 Apr 2017 16:50:28 -0400
Subject: [PATCH] [JENKINS-43361] Unreproducible NPE.

---
 .../jenkinsci/plugins/workflow/cps/CpsFlowExecution.java   | 2 +-
 .../org/jenkinsci/plugins/workflow/cps/CpsStepContext.java | 7 ++++++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/main/java/org/jenkinsci/plugins/workflow/cps/CpsFlowExecution.java b/src/main/java/org/jenkinsci/plugins/workflow/cps/CpsFlowExecution.java
index abd324469..05573f90c 100644
--- a/src/main/java/org/jenkinsci/plugins/workflow/cps/CpsFlowExecution.java
+++ b/src/main/java/org/jenkinsci/plugins/workflow/cps/CpsFlowExecution.java
@@ -694,7 +694,7 @@ public void waitForSuspension() throws InterruptedException, ExecutionException
         g.scheduleRun().get();
     }
 
-    public synchronized FlowHead getFlowHead(int id) {
+    public synchronized @CheckForNull FlowHead getFlowHead(int id) {
         return heads.get(id);
     }
 
diff --git a/src/main/java/org/jenkinsci/plugins/workflow/cps/CpsStepContext.java b/src/main/java/org/jenkinsci/plugins/workflow/cps/CpsStepContext.java
index f2b39c281..e87f8b98c 100644
--- a/src/main/java/org/jenkinsci/plugins/workflow/cps/CpsStepContext.java
+++ b/src/main/java/org/jenkinsci/plugins/workflow/cps/CpsStepContext.java
@@ -383,7 +383,12 @@ private void scheduleNextRun() {
 
             final List<FlowNode> parents = new ArrayList<FlowNode>();
             for (int head : bodyHeads) {
-                parents.add(flow.getFlowHead(head).get());
+                FlowHead flowHead = flow.getFlowHead(head);
+                if (flowHead != null) {
+                    parents.add(flowHead.get());
+                } else {
+                    LOGGER.log(Level.WARNING, "Could not find flow head #{0}", head);
+                }
             }
 
             flow.runInCpsVmThread(new FutureCallback<CpsThreadGroup>() {