A reference exception is thrown when an attempt is made to access a resource that is already in use. In the most common scenario, this occurs when an object is created and its reference count is not correctly initialized. For example, bitlife a new object may be created, and its reference count may be set to zero. When the object is later accessed, it will be found to be in use, and the exception will be thrown. 

Open script by double clicking in the folder. Don't open it by double clicking on the inspector.

Same here Unity 2019.2.5f1 & Vuforia 8.5.9, Reverted to Vuforia 8.3.9 Same issue.

This is incredible, every single time I'm using vuforia (and it's been years) I get a bunch of errors straight out of the box... Could you please keep a log on which version of vuforia to use with which version of unity maybe ? I've been a fan for years, but what a pain in the ass to get it started.... It gets really frustrating tbh.

On top of that I get huge drift and completely useless trackability if I enable track device pose. The 3D object doesn't even stick to the tracker... If I unenable it, it's super stable...

Same problem +1

Unity 2019.1

Vuforia 8.3.8

Same problem here

Unity 2019.2.0.f1

Vuforia 8.5.8

I'm having the same problem.

ullReferenceException: Object reference not set to an instance of an object

Vuforia.EditorClasses.WorkerToMainScheduler.UpdateFromMainThread () (at <863340cee03640148af16e5524363348>:0)

UnityEditor.EditorApplication.Internal_CallUpdateFunctions () (at C:/buildslave/unity/build/Editor/Mono/EditorApplication.cs:303)

Joe

Unity 2018.3.5f1

Vuforia 8.0.10

Same problem, error message displayed in the Console :

NullReferenceException: Object reference not set to an instance of an object

Vuforia.EditorClasses.ImageTargetEditor.DrawPredefinedTargetInspectorUI (System.Boolean typeChanged) (at <863340cee03640148af16e5524363348>:0)

Vuforia.EditorClasses.ImageTargetEditor.OnInspectorGUI () (at <863340cee03640148af16e5524363348>:0)

UnityEditor.InspectorWindow.DoOnInspectorGUI (System.Boolean rebuildOptimizedGUIBlock, UnityEditor.Editor editor, System.Boolean wasVisible, UnityEngine.Rect& contentRect) (at C:/buildslave/unity/build/Editor/Mono/Inspector/InspectorWindow.cs:1625)

UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

It happens randomly, for example after modifying some code in Visual Studio and coming back to Unity. No explanation.