Fix a SIGSEGV

internal/ordoor/ordoor.go

@@ -7,6 +7,7 @@ package ordoor
 import (
 	"fmt"
 	"log"
+	"sync"
 	"time"
 
 	"github.com/hajimehoshi/ebiten/v2"
@@ -28,7 +29,8 @@ type Ordoor struct {
 	win    *ui.Window
 
 	// Relevant to interface state
-	flow *flow.Flow
+	flow     *flow.Flow
+	flowOnce sync.Once
 
 	// FIXME: should be put inside flow
 	// If this is set, we display it instead of flow
@@ -178,6 +180,7 @@ func (o *Ordoor) Update(screenX, screenY int) error {
 }
 
 func (o *Ordoor) Draw(screen *ebiten.Image) error {
+
 	if pic := o.pic; pic != nil {
 		// Scale the picture to the screen and draw it
 		scaleX := float64(screen.Bounds().Dx()) / float64(pic.Bounds().Dx())
@@ -190,7 +193,11 @@ func (o *Ordoor) Draw(screen *ebiten.Image) error {
 		return nil
 	}
 
-	return o.flow.Draw(screen)
+	if o.flow != nil {
+		return o.flow.Draw(screen)
+	}
+
+	return nil // Draw() may be called before Update()
 }
 
 func (o *Ordoor) Cursor() (*ebiten.Image, *ebiten.DrawImageOptions, error) {