GUI freezes if you open a new instance, add some text to a buffer, yank it, undo the changes, then try to quit

[yorickpeterse]

Describe the bug

This is an awfully specific chain of events, and I suspect it can be narrowed down to something simpler, but the problem is as follows:

1. Run the GUI
2. In the new empty buffer, type foo in insert mode
3. Exit insert mode
4. Press yy to yank the line
5. Run :q! to exit
6. Observe how the GUI hangs

This can be seen in action here:

bug.webm

Technical information (please complete the following information):

• OS: Arch Linux in a container, on a Fedora 39 Silverblue host
• Neovim version: 0.9.4
• Neovim-Gtk build version: v1.0.1-168-g50f27f5