segmentation fault when program is closed

**Describe the bug**

In wayland, using egui-winit with the `clipboard` feature causes segmentation fault when the program is closed. Program starts fine and runs fine but when closed, segmentation fault occurs. This is reproducible with the [pure_glow](https://github.com/emilk/egui/blob/main/crates/egui_glow/examples/pure_glow.rs) example by running the example with the `clipboard` feature included.

**To Reproduce**
Steps to reproduce the behavior:
1. Run the `pure_glow` example with `clipboard` feature
```sh
cargo run -p egui_glow --example pure_glow --features=winit,egui/default_fonts,clipboard
```
2. After the program runs and window appears, close the program, i. e., click on Quit in the UI or close it with ctrl + c.
3. segmentation fault (core dumped) is shown

**Expected behavior**

Program should close without segmentation fault.

**Screenshots**

**Desktop (please complete the following information):**
- OS: Arch Linux with sway
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**Smartphone (please complete the following information):**
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**Additional context**

It probably has something to do with [smithay-clipboard](https://crates.io/crates/smithay-clipboard), because the debugger shows the following

Start with the pure_glow example and reproduce the failure using the documented cargo command on Wayland with the clipboard feature enabled. Inspect the shutdown path and the smithay-clipboard interaction, including the debugger evidence in the issue. Done means the example closes normally without a segmentation fault.

Written by the indexing model from the issue text.