NullReferenceException: Object reference not set to an instance of an object
UnityEditor.TreeViewDragging.DragElement (UnityEditor.TreeViewItem targetItem, Rect targetItemRect, Boolean firstItem) (at C:/BuildAgent/work/d63dfc6385190b60/Editor/Mono/GUI/TreeView/TreeViewDragging.cs:201)
UnityEditor.TreeView.HandleUnusedMouseEventsForNode (Rect rect, UnityEditor.TreeViewItem item, Boolean firstItem) (at C:/BuildAgent/work/d63dfc6385190b60/Editor/Mono/GUI/TreeView/TreeView.cs:304)
UnityEditor.TreeView.OnGUI (Rect rect, Int32 keyboardControlID) (at C:/BuildAgent/work/d63dfc6385190b60/Editor/Mono/GUI/TreeView/TreeView.cs:408)
UnityEditor.SceneHierarchyWindow.DoTreeView
201行，对象的引用未设置到对象的实例。应该是引用的时候可能没有这个实例或者物体，引用出错了。304不知道，看着像UnityEditor.TreeView.HandleUnusedMouseEventsForNode函数后面的Rect rect, UnityEditor.TreeViewItem item, Boolean firstItem三个参数你弄错了。408跟304差不多UnityEditor.TreeView.OnGUI函数后面两个参数你检查检查。
看第一个错误的意思先