ARTrackableManager spamming NullReferenceException

[andyb-unity]

FYI This looks like a question for Microsoft at first glance. Note our FAQ :

How to do X using HoloLens?
Unity does not implement AR Foundation support for HoloLens. Microsoft owns and maintains their AR Foundation provider plug-in and build tools. For any questions regarding HoloLens other than specifically the UnityEngine or UnityEditor API’s, please refer to the Microsoft Mixed Reality forums: https://techcommunity.microsoft.com/t5/mixed-reality/ct-p/MicrosoftMixedReality