LayerChooser: Options menu has multiple flaws

[dopenguin]

Describe the bug

1. When deselecting sub-layers, the last layer that is deselected is still shown in the map.
2. After deselecting a layer, going back to the main layer chooser menu and then opening the options again, all layers are selected again.

Expected behavior

1. All layers can be deselected. The layer itself would then be shown as deselected as well.
2. The selection state of sub-layers is always represented no matter how often one moves in the menu.

Steps to reproduce

See above.

[dopenguin]

Fixed by 0540adb