In note editor's preview, let the user know which cards are empty

Please don't start working on this issue until another maintainer approved the change I request. Everybody else is welcome to comment as I'd be interested to know whether other people want the feature I'm requesting

How to reproduce:
* open the add card/note editor
* optional: tap some content. Enough to have some cards displayed and some cards empty
* tap the eye to open the previewer

What I'd like is that the cards that are empty have a distinct style. For example striking their name.
The use case is that when I want to preview my cards, I want to be able to easily check the cards that will actually be generated. Knowing which ones are empty and which are not would ensure that I don't have to tap on all of them