Check for panner_shell rather than panner before

connecting to it.  This means that we connect to mono
routes (without panners) so that if they do get panners
we find out about it.  Should help with #5093.


git-svn-id: svn://localhost/ardour2/branches/3.0@13190 d708f5d6-7413-0410-9779-e7cbd77b26cf

gtk2_ardour/audio_time_axis.cc

@@ -105,7 +105,7 @@ AudioTimeAxisView::set_route (boost::shared_ptr<Route> rt)
 		create_automation_child (GainAutomation, false);
 	}
 
-	if (_route->panner()) {
+	if (_route->panner_shell()) {
 		_route->panner_shell()->Changed.connect (*this, invalidator (*this),
                                                          boost::bind (&AudioTimeAxisView::ensure_pan_views, this, false), gui_context());
 	}