if WorldAnchorObject dont have parent, null exception occur.

ohmura · ohmura · commit b2e46e5ab47d · 2018-10-17T13:04:55.000+09:00
change to check to be anchor.gameobject.transform.parent null
diff --git a/Assets/HoloToolkit/Common/Scripts/WorldAnchorManager.cs b/Assets/HoloToolkit/Common/Scripts/WorldAnchorManager.cs
@@ -324,7 +324,7 @@ public void RemoveAllAnchors()
             for (var i = 0; i < anchors.Length; i++)
             {
                 // Don't remove SpatialMapping anchors if exists
-                if (spatialMappingManager != null && anchors[i].gameObject.transform.parent.gameObject == spatialMappingManager.gameObject)
+                if (spatialMappingManager != null && anchors[i].gameObject.transform.parent != null && anchors[i].gameObject.transform.parent.gameObject == spatialMappingManager.gameObject)
                 { continue; }
 
                 // Let's check to see if there are anchors we weren't accounting for.

Original file line number	Diff line number	Diff line change
`@@ -324,7 +324,7 @@ public void RemoveAllAnchors()`
`324`	`324`	`for (var i = 0; i < anchors.Length; i++)`
`325`	`325`	`{`
`326`	`326`	`// Don't remove SpatialMapping anchors if exists`
`327`		`- if (spatialMappingManager != null && anchors[i].gameObject.transform.parent.gameObject == spatialMappingManager.gameObject)`
	`327`	`+ if (spatialMappingManager != null && anchors[i].gameObject.transform.parent != null && anchors[i].gameObject.transform.parent.gameObject == spatialMappingManager.gameObject)`
`328`	`328`	`{ continue; }`
`329`	`329`
`330`	`330`	`// Let's check to see if there are anchors we weren't accounting for.`