Image disappears when sprite is changed

[prostolyubo]

If we change the sprite of the Image (manually or programatically) the whole image disappears.
One needs to call .Validate() and .Refresh() every time a sprite changes.

But this adds unnecessary dependencies and I believe the ImageWithRoundedCorners should handle that. Even better if there was no need to do that at all - but I am not really sure why it breaks. Material stays the same after all.