From 2b8912f7901ff00aadc20e01371b4b8a53971967 Mon Sep 17 00:00:00 2001
From: Carl Hetherington <carl@carlh.net>
Date: Thu, 14 Jun 2012 11:45:10 +0000
Subject: [PATCH] Hopefully fix race between engine being halted and butler
 being destroyed.

git-svn-id: svn://localhost/ardour2/branches/3.0@12722 d708f5d6-7413-0410-9779-e7cbd77b26cf
---
 libs/ardour/session.cc           | 2 ++
 libs/ardour/session_transport.cc | 8 +++++---
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/libs/ardour/session.cc b/libs/ardour/session.cc
index 9e46f38f6a..9f8d0808af 100644
--- a/libs/ardour/session.cc
+++ b/libs/ardour/session.cc
@@ -248,6 +248,8 @@ Session::destroy ()
 
 	_butler->drop_references ();
 	delete _butler;
+	_butler = 0;
+	
 	delete midi_control_ui;
 	delete _all_route_group;
 
diff --git a/libs/ardour/session_transport.cc b/libs/ardour/session_transport.cc
index 5fef402d9f..7c23e2aee7 100644
--- a/libs/ardour/session_transport.cc
+++ b/libs/ardour/session_transport.cc
@@ -1476,9 +1476,11 @@ Session::engine_halted ()
 	   the picture.
 	*/
 
-	g_atomic_int_set (&_butler->should_do_transport_work, 0);
-	set_post_transport_work (PostTransportWork (0));
-	_butler->stop ();
+	if (_butler) {
+		g_atomic_int_set (&_butler->should_do_transport_work, 0);
+		set_post_transport_work (PostTransportWork (0));
+		_butler->stop ();
+	}
 
 	realtime_stop (false, true);
 	non_realtime_stop (false, 0, ignored);