Fixed an error thrown on shutdown when a subsystem was already destroyed.
Previously, when [adding](xref:UnityEngine.XR.ARFoundation.AREnvironmentProbeManager.AddEnvironmentProbe\(UnityEngine.Pose,UnityEngine.Vector3,UnityEngine.Vector3\)) an [environment probes](xref:UnityEngine.XR.ARFoundation.AREnvironmentProbe), the world space position of the new probe was passed to the underlying AR framework instead of the session-relative pose. This would place the environment probe in the incorrect position and/or orientation if the [session origin](xref:UnityEngine.XR.ARFoundation.ARSessionOrigin) was not at the origin.
