switch: Use the right state when querying padding
switch: Use the right state when querying padding

We were using the state of the widget node, not the state of the slider
node.

This caused layout loops due to invalidations.

grubersjoe/adwaita,grubersjoe/adwaita,grubersjoe/adwaita,alexlarsson/gtk,alexlarsson/gtk,grubersjoe/adwaita,alexlarsson/gtk,alexlarsson/gtk,alexlarsson/gtk,grubersjoe/adwaita,alexlarsson/gtk,alexlarsson/gtk,grubersjoe/adwaita,grubersjoe/adwaita,grubersjoe/adwaita,alexlarsson/gtk