From b61ee091e843571e546146095842a0bf049a8910 Mon Sep 17 00:00:00 2001
From: Ufuk Celebi <uce@apache.org>
Date: Fri, 24 Mar 2017 12:24:19 +0100
Subject: [PATCH] [FLINK-6182] Fix possible NPE in SourceStreamTask

---
 .../flink/streaming/runtime/tasks/SourceStreamTask.java       | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/tasks/SourceStreamTask.java b/flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/tasks/SourceStreamTask.java
index 63b40ad8957cb..18291408d0e35 100644
--- a/flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/tasks/SourceStreamTask.java
+++ b/flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/tasks/SourceStreamTask.java
@@ -58,6 +58,8 @@ protected void run() throws Exception {
 	
 	@Override
 	protected void cancelTask() throws Exception {
-		headOperator.cancel();
+		if (headOperator != null) {
+			headOperator.cancel();
+		}
 	}
 }