NullReferenceException Object reference not set to an instance of an objectUnityEditorSceneHierarchyInit at CbuildslaveunitybuildEditorMonoSceneHierarchycs259UnityEditorSceneHierarchyget_treeView at

This error message is a common exception in C# and Unity when the program attempts to reference an object that is null or does not exist. In this case, the error message indicates that there is an issue with the SceneHierarchy class. It may be trying to access a variable or method that has not been initialized or instantiated yet.

To solve this issue, you can try the following:

1. Check if all the necessary objects and components are present in the scene. Make sure that you have not deleted any required assets or game objects.

2. Check if the object reference is null before using it. You can use a null check to ensure that the object exists before attempting to access it.

3. Check if there are any errors in the console window that may be related to this issue. Sometimes, there may be other errors that are causing this exception to occur.

4. Try restarting Unity and reloading the scene. This may help to refresh any cached data or scripts that may be causing the issue.

5. If none of these solutions work, you may need to debug the code further or seek help from the Unity community or support team