Use the only ZStack one state for indicator, instead of removing that indicator view from hierarchy

[dreampiggy]

Fix for annoying bugs because the fact:

when writting the if else code with a Binding object, it will query the WebImage.body again.

This means, another new WebImage struct will be created, and receive a ImageManger.load (ImageManger is a class, which means they share the same state !). So the state mass up.

Using ZStack without changes will not cause the WebImage to be re-generaetd. This is the simplest solution.