From e94e313185d003181ad874136d9b09608006035a Mon Sep 17 00:00:00 2001
From: ambientlabs <darren@ambientlabs.org>
Date: Mon, 8 Jun 2020 10:02:46 -1000
Subject: [PATCH] NPE fix for closing with pending AckClosure(s) on Android

---
 src/main/java/io/nats/streaming/StreamingConnectionImpl.java | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/main/java/io/nats/streaming/StreamingConnectionImpl.java b/src/main/java/io/nats/streaming/StreamingConnectionImpl.java
index 6a410c2..1cf8242 100644
--- a/src/main/java/io/nats/streaming/StreamingConnectionImpl.java
+++ b/src/main/java/io/nats/streaming/StreamingConnectionImpl.java
@@ -354,7 +354,8 @@ void close(boolean silent) throws IOException, InterruptedException {
                     for (AckClosure ac : this.pubAckMap.values()) {
                         ac.ackTask.cancel();
 
-                        if (!ac.ch.isEmpty()) {
+                        // Note: Providing an Ack Handler when publishing to STAN (on Android) can result in NPEs during some closing scenarios
+                        if (ac.ch != null && !ac.ch.isEmpty()) {
                             ac.ch.take();
                         }
                     }