the example serial_windows doesn't work as expected

**Describe the bug**
Can't destroy window when **_main_** doesn't end, the window always exists

**To Reproduce**
just run the example [serial_windows](https://github.com/emilk/egui/tree/master/examples/serial_windows)

**Expected behavior**
Immediately destroys the window when the close button is pressed, and the window can be created repeatedly.

**Desktop (please complete the following information):**
- OS: Arch Linux x86_64
- wm: sway v1.9
- egui 78dfdb36

Someone mentioned the [issue](https://github.com/emilk/egui/issues/2892) before and it appeared to be resolved. But now the problem has reappeared and has been [encountered](https://github.com/emilk/egui/issues/2892#issuecomment-2042981079) by others recently

Start by running the examples/serial_windows example and reproducing the close-and-recreate sequence described in the issue. Trace the window lifecycle involved when main does not end, using issue #2892 and its linked comment as context. Done means closing the window destroys it immediately and allows it to be created repeatedly.

Written by the indexing model from the issue text.