update engine dialog UI state

fixes crash when jack is started externally
and the dialog is displayed later.
The current state e.g. avail buffer sizes is not
are queried from the backend, Apply,OK -> crash
because the dropdown is empty) 

1 files changed, 1 insertions, 0 deletions

diff --git a/gtk2_ardour/engine_dialog.cc b/gtk2_ardour/engine_dialog.cc
index 387d705a9c..942de79b1b 100644
--- a/gtk2_ardour/engine_dialog.cc
+++ b/gtk2_ardour/engine_dialog.cc
@@ -304,6 +304,7 @@ void
 EngineControl::on_show ()
 {
 	ArdourDialog::on_show ();
+	device_changed ();
 	ok_button->grab_focus();
 }