stop crash when existing a session/quitting without a monitor section

git-svn-id: svn://localhost/ardour2/branches/3.0@6810 d708f5d6-7413-0410-9779-e7cbd77b26cf

diff --git a/gtk2_ardour/mixer_ui.cc b/gtk2_ardour/mixer_ui.cc
index da330c25faca9314a4a1df157044ed30e4b2aec7..618d1bbe36b75a6caa0dc69a2457547e8e22e581 100644 (file)
--- a/gtk2_ardour/mixer_ui.cc
+++ b/gtk2_ardour/mixer_ui.cc
@@ -538,7 +538,9 @@ Mixer_UI::session_going_away ()
                delete (*i);
        }
 
-        _monitor_section->tearoff().hide_visible ();
+        if (_monitor_section) {
+                _monitor_section->tearoff().hide_visible ();
+        }
 
        strips.clear ();