From 5970bbb6bfb7a09e4b97e9134fdaa06513b12e35 Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Tue, 23 Apr 2013 07:06:11 -0600
Subject: [PATCH] fix NACK fix

Fixup for 74fb6feb45.
---
 src/racket/src/thread.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/racket/src/thread.c b/src/racket/src/thread.c
index 7e77ba71b7..231ca2a059 100644
--- a/src/racket/src/thread.c
+++ b/src/racket/src/thread.c
@@ -6534,7 +6534,7 @@ static void escape_during_sync(Syncing *syncing)
 
   syncing->thread = NULL;
 
-  if (p->sync_box)
+  if (p && p->sync_box)
     scheme_post_sema_all(p->sync_box);
   scheme_post_syncing_nacks(syncing);