More robust midi implementation

src/app.rs

@@ -118,12 +118,18 @@ impl App {
                 quantum: link.quantum(),
             },
             midi: crate::settings::MidiSettings {
-                output_device: self.midi.selected_output.and_then(|idx| {
-                    crate::midi::list_midi_outputs().get(idx).map(|d| d.name.clone())
-                }),
-                input_device: self.midi.selected_input.and_then(|idx| {
-                    crate::midi::list_midi_inputs().get(idx).map(|d| d.name.clone())
-                }),
+                output_devices: {
+                    let outputs = crate::midi::list_midi_outputs();
+                    self.midi.selected_outputs.iter()
+                        .map(|opt| opt.and_then(|idx| outputs.get(idx).map(|d| d.name.clone())).unwrap_or_default())
+                        .collect()
+                },
+                input_devices: {
+                    let inputs = crate::midi::list_midi_inputs();
+                    self.midi.selected_inputs.iter()
+                        .map(|opt| opt.and_then(|idx| inputs.get(idx).map(|d| d.name.clone())).unwrap_or_default())
+                        .collect()
+                },
             },
         };
         settings.save();