fix logic errors in duplicate tracks dialog

gtk2_ardour/ardour_ui.cc

@@ -3759,9 +3759,11 @@ ARDOUR_UI::start_duplicate_routes ()
 		duplicate_routes_dialog = new DuplicateRouteDialog;
 	}
 
-	if (duplicate_routes_dialog->restart ()) {
-		duplicate_routes_dialog->present ();
+	if (duplicate_routes_dialog->restart (_session)) {
+		return;
 	}
+
+	duplicate_routes_dialog->present ();
 }
 
 void

gtk2_ardour/duplicate_routes_dialog.cc

@@ -56,8 +56,14 @@ DuplicateRouteDialog::DuplicateRouteDialog ()
 }
 
 int
-DuplicateRouteDialog::restart ()
+DuplicateRouteDialog::restart (Session* s)
 {
+	if (!s) {
+		return -1;
+	}
+
+	set_session (s);
+
 	TrackSelection& tracks  (PublicEditor::instance().get_selection().tracks);
 	uint32_t ntracks = 0;
 	uint32_t nbusses = 0;
@@ -91,9 +97,11 @@ DuplicateRouteDialog::restart ()
 	   which is what we really want to happen here.
 	*/
 
-	if (ntracks == 0) {
+	if (playlist_button_box.get_parent()) {
 		get_vbox()->remove (playlist_button_box);
-	} else {
+	}
+
+	if (ntracks > 0) {
 		get_vbox()->pack_end (playlist_button_box, false, false);
 	}
 

gtk2_ardour/duplicate_routes_dialog.h

@@ -30,6 +30,10 @@
 
 #include "ardour_dialog.h"
 
+namespace ARDOUR {
+class Session;
+}
+
 class Editor;
 
 class DuplicateRouteDialog : public ArdourDialog
@@ -37,7 +41,7 @@ class DuplicateRouteDialog : public ArdourDialog
   public:
 	DuplicateRouteDialog ();
 
-	int restart ();
+	int restart (ARDOUR::Session*);
 
   private:
 	Gtk::Entry name_template_entry;