Minor bug: zoom UI gets out of sync after scanning

[denilsonsa]

How to reproduce:

1. Go to the Scan screen.
2. Use the slider to zoom in.
3. Scan any barcode.
4. Go back.

What happens: the zoom slider is reset back to zero, but the camera image is still zoomed in. (Interacting with the slider solves the issue.)

What should happen:

• The zoom slider and the camera zoom should always be in sync.
• Ideally, the zoom ia remembered.
• Not ideally, but acceptable, the zoom is reset each time we go back to the Scan screen.

[FrostKiwi]

Can confirm this for version 1.9.