-e: if you drop a texture into a substance it throws an error

-repro:
--open attached project
--select Bitmap2Material_2 in the B3M folder
--scroll down to the Bitmap Diffuse
--click on the assets folder
--drag & drop the brick texture onto the Bitmap Diffuse, don't release the left mouse button
--NOTICE errors being thrown:

Destroying object multiple times. Don't use DestroyImmediate on the same object in OnDisable or OnDestroy.
UnityEditor.Undo:Internal_CallUndoRedoPerformed()