`new MotionController(...)` throws exception for "transient-pointer" with ["generic-button"] but no gamepad

[hybridherbst]

Describe the bug
Transient pointers on Vision OS currently have this information:

{
  targetRayMode: "transient-pointer",
  profiles: ["generic-button"],
}

Unfortunately that causes an exception in new MotionController(), likely because updateGamepad() is called with undefined:
https://github.com/immersive-web/webxr-input-profiles/blob/main/packages/motion-controllers/src/component.d.ts#L22

Expected behavior
No exception

Smartphone (please complete the following information):

• Device: visionPro
• OS: visionOS
• Browser Safari