My Scene window went black and is throwing a console error, now I can't see anything

I have uninstalled and reinstalled Unity (2019.4.15f1, the latest recommended build), and created new scenes, to no avail. Whenever I try to bring up the Scene window I get the following console error:

NullReferenceException: Object reference not set to an instance of an object
UnityEditor.HostView.DeregisterSelectedPane (System.Boolean clearActualView, System.Boolean sendEvents) (at :0)
UnityEditor.HostView.SetActualViewInternal (UnityEditor.EditorWindow value, System.Boolean sendEvents) (at :0)
UnityEditor.DockArea.SetSelectedPrivate (System.Int32 value, System.Boolean sendEvents) (at :0)
UnityEditor.DockArea.set_selected (System.Int32 value) (at :0)
UnityEditor.EditorWindow.ShowTab () (at :0)
UnityEditor.EditorWindow.Focus () (at :0)
UnityEditor.EditorWindow.GetWindowPrivate (System.Type t, System.Boolean utility, System.String title, System.Boolean focus) (at :0)
UnityEditor.EditorWindow.GetWindow (System.Type t, System.Boolean utility, System.String title, System.Boolean focus) (at :0)
UnityEditor.EditorWindow.GetWindow[T] (System.Boolean utility, System.String title, System.Boolean focus) (at :0)
UnityEditor.EditorWindow.GetWindow[T] () (at :0)
UnityEditor.CreateBuiltinWindows.ShowSceneView () (at :0)
UnityEditor.EditorApplication:Internal_CallGlobalEventHandler()

I think this happened after I imported a package that itself updated the Package Manager. But I can’t be sure of this. I’ve been doing a lot in Unity lately.

This is all I ever see in the editor itself:

screenshot of Unity editor window

Well, I managed to fix it by right-clicking on the Packages folder and clicking “Reimport All”:

screenshot demonstrating menu option to Reimport All packages