X11: Crash when resizing winit example window

[FreeFull]

When running softbuffer's winit example under X11, it seems it's not guaranteed that window.inner_size(); matches the latest processed WindowEvent::Resized. This can lead to an index out of bounds panic in the example's redraw code.

To reproduce, in an X11 environment:

cargo run --example winit

and then resize the window rapidly. It's also reproducible with --release, but not as easily. I'm not actually sure if this should be considered a bug with the example, or with winit itself.