I was wondering the same thing, and read your post that I can just highlight and remove the url and hit save.
But I'm worried my site visitors updating their posts won't know to do that. Is there some function with jquery where it could add a "Reset Image" or "Delete Image" button where it would just clear the url out, with one click for them?
And just to clarify, I'm talking about in the same admin cpt area that johnH-2 was referring to (not CRED).
Thanks for your help!