fix(sointu-vsti): VST crashed due to Model.MIDI being nil

cmd/sointu-track/main.go

@@ -54,7 +54,8 @@ func main() {
 		recoveryFile = filepath.Join(configDir, "Sointu", "sointu-track-recovery")
 	}
 	model, player := tracker.NewModelPlayer(cmd.MainSynther, recoveryFile)
-	model.MIDI = gomidi.NewContext()
+	midiContext := gomidi.NewContext()
+	model.MIDI = midiContext
 	defer model.MIDI.Close()
 	if a := flag.Args(); len(a) > 0 {
 		f, err := os.Open(a[0])
@@ -64,7 +65,7 @@ func main() {
 		f.Close()
 	}
 	tracker := gioui.NewTracker(model)
-	audioCloser := audioContext.Play(&PlayerAudioSource{player, model.MIDI})
+	audioCloser := audioContext.Play(&PlayerAudioSource{player, midiContext})
 	go func() {
 		tracker.Main()
 		audioCloser.Close()

cmd/sointu-vsti/main.go

@@ -17,12 +17,22 @@ import (
 	"pipelined.dev/audio/vst2"
 )
 
-type VSTIProcessContext struct {
-	events     []vst2.MIDIEvent
-	eventIndex int
-	host       vst2.Host
+type (
+	VSTIProcessContext struct {
+		events     []vst2.MIDIEvent
+		eventIndex int
+		host       vst2.Host
+	}
+
+	NullMIDIContext struct{}
+)
+
+func (m *NullMIDIContext) ListInputDevices() func(yield func(tracker.MIDIDevice) bool) {
+	return func(yield func(tracker.MIDIDevice) bool) {}
 }
 
+func (m *NullMIDIContext) Close() {}
+
 func (c *VSTIProcessContext) NextEvent() (event tracker.MIDINoteEvent, ok bool) {
 	for c.eventIndex < len(c.events) {
 		ev := c.events[c.eventIndex]
@@ -63,6 +73,8 @@ func init() {
 			recoveryFile = filepath.Join(configDir, "sointu", "sointu-vsti-recovery-"+hex.EncodeToString(randBytes))
 		}
 		model, player := tracker.NewModelPlayer(cmd.MainSynther, recoveryFile)
+		model.MIDI = &NullMIDIContext{}
+
 		t := gioui.NewTracker(model)
 		tracker.Bool{BoolData: (*tracker.InstrEnlarged)(model)}.Set(true)
 		go t.Main()

tracker/model.go

@@ -126,7 +126,6 @@ type (
 	MIDIContext interface {
 		ListInputDevices() func(yield func(MIDIDevice) bool)
 		Close()
-		PlayerProcessContext
 	}
 
 	MIDIDevice interface {