Change `window_min_size` from `Size<Pixels>` to `Option<Size<Pixels>>` (#13501)

Now we can set `window_min_size` to `None` instead of `Size::default()`.
I think this makes more sense.

Release Notes:

- N/A
d1a55d64a8张小白 committed on 6/25/2024, 6:09:08 PM· committed by GitHubparentdb06244
5 files changedLine totals unavailable