Add stubs for unknown widget types

internal/ui/buttons.go

@@ -14,6 +14,8 @@ func init() {
 }
 
 // A button without hover animation
+// FIXME: Keyboard.mnu has TypeSimpleButton instances that seem to include a
+// hover in the SpriteId field
 type button struct {
 	path string
 
@@ -34,6 +36,11 @@ type mainButton struct {
 }
 
 func registerSimpleButton(d *Driver, r *menus.Record) error {
+	// FIXME: LevelPly.mnu specifies a menu oddly. This tweak gets us past it
+	if d.Name == "levelply" && r.Id == 2 {
+		return nil
+	}
+
 	return registerButton(d, r, r.SpriteId[0])
 }