The check for a VR device does not happen at run time. Hence, when the app runs of a Windows 10 device that is NOT a HoloLens, it will will crash. This happens for instance when the Windows App Certification Kit runs. Result: the WACK lists a boatload of errors that will never happen when the app is actually deployed to a HoloLens, causing confusing for developers. Also, it prevents the app from running on a normal PC.

LocalJoost · LocalJoost · commit 80c2c6d2536d · 2017-01-04T11:08:36.000+01:00
diff --git a/Assets/HoloToolkit/SpatialMapping/Scripts/SpatialMappingManager.cs b/Assets/HoloToolkit/SpatialMapping/Scripts/SpatialMappingManager.cs
@@ -186,7 +186,7 @@ public bool IsObserverRunning()
         /// </summary>
         public void StartObserver()
         {
-#if UNITY_EDITOR
+#if UNITY_EDITOR || UNITY_UWP
             // Allow observering if a device is present (Holographic Remoting)
             if (!UnityEngine.VR.VRDevice.isPresent) return;
 #endif

Original file line number	Diff line number	Diff line change
`@@ -186,7 +186,7 @@ public bool IsObserverRunning()`
`186`	`186`	`/// </summary>`
`187`	`187`	`public void StartObserver()`
`188`	`188`	`{`
`189`		`-#if UNITY_EDITOR`
	`189`	`+#if UNITY_EDITOR \|\| UNITY_UWP`
`190`	`190`	`// Allow observering if a device is present (Holographic Remoting)`
`191`	`191`	`if (!UnityEngine.VR.VRDevice.isPresent) return;`
`192`	`192`	`#endif`