editing express entry - problem with images

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I have setup a product-catalog using express. (using the tutorials/videos from the concrete5-docs) The detail view consists of product-details and some product-images. The form gets displayed in the front-end, so authorised users can add new entries. Everything works fine except when editing/updating entries (in the backend) all the images get deleted.

It kinda makes sense to my why... since the form displays a html-file input for the images which is empty when editing an entry. But I can't figure out how to solve this problem.

Another somewhat related question:
Is it possible to setup an edit-form in the frontend as well? In theory it would have to be a form that gets populated with the data from the corresponding express-object, right? How would I do that?