From 1e2ead0a126b0034ee400f1c440e6d6226cd8b83 Mon Sep 17 00:00:00 2001
From: David Pursehouse <dpursehouse@collab.net>
Date: Thu, 31 Aug 2017 10:02:37 +0900
Subject: [PATCH] StreamEvents: Fix NPE when invoking the command with --help

When executing the command:

  ssh user@host gerrit stream-events --help

the onExit and destroy methods attempt to remove the event listener
registration which has not been initialized, resulting in NPE and
the command hanging.

Add null checks to prevent this.

Change-Id: I1b9ccd41d017e62f0a4206114ab15faa6ed8e000
---
 .../google/gerrit/sshd/commands/StreamEvents.java    | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/gerrit-sshd/src/main/java/com/google/gerrit/sshd/commands/StreamEvents.java b/gerrit-sshd/src/main/java/com/google/gerrit/sshd/commands/StreamEvents.java
index 1c0a4247ac..76d15f7c1e 100644
--- a/gerrit-sshd/src/main/java/com/google/gerrit/sshd/commands/StreamEvents.java
+++ b/gerrit-sshd/src/main/java/com/google/gerrit/sshd/commands/StreamEvents.java
@@ -169,9 +169,15 @@ final class StreamEvents extends BaseCommand {
             .create();
   }
 
+  private void removeEventListenerRegistration() {
+    if (eventListenerRegistration != null) {
+      eventListenerRegistration.remove();
+    }
+  }
+
   @Override
   protected void onExit(final int rc) {
-    eventListenerRegistration.remove();
+    removeEventListenerRegistration();
 
     synchronized (taskLock) {
       done = true;
@@ -182,7 +188,7 @@ final class StreamEvents extends BaseCommand {
 
   @Override
   public void destroy() {
-    eventListenerRegistration.remove();
+    removeEventListenerRegistration();
 
     final boolean exit;
     synchronized (taskLock) {
@@ -230,7 +236,7 @@ final class StreamEvents extends BaseCommand {
         // destroy() above, or it closed the stream and is no longer
         // accepting output. Either way terminate this instance.
         //
-        eventListenerRegistration.remove();
+        removeEventListenerRegistration();
         flush();
         onExit(0);
         return;