The examples crash if you minimize the window

[takahirox]

The examples crash if you minimize the window.

How to reproduce

1. $ cargo run --example triangle
2. Minimize the window
3. Crashes

The error log

thread 'main' panicked at 'Error in Surface::configure: Both `Surface` width and height must be non-zero. Wait to recreate the `Surface` until the window has non-zero area.', C:\Users\Takahiro\.cargo\git\checkouts\wgpu-53e70f8674b08dd4\c3d9068\wgpu\src\backend\direct.rs:197:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
error: process didn't exit successfully: `target\debug\examples\rotation.exe` (exit code: 101)

[michalusio]

Hi!

The bug is happening because minimizing the window sends a Resize event with size (0, 0) which crashes the Surface configuration.

That can be fixed by either checking the size in the example and not changing the surface's size (and probably not rendering while minimized?) or it could be handled by the library itself.

If you want to, I can take a look and add a "minimized" flag to the renderer that would handle resizing to (0, 0), and would not render while minimized.