Adding An Empty Script to DropDown Causing NullReferenceExeption Error

Unity Engine
,
1

Hi, So I have a drop down TMP, that when I add a script to it, even though its an empty new script, I start getting the following error:

Thanks in advance

2

Additional note: Removing the script does not get rid of the error, I would have to remove it by CTRL + Z (Undo).