minimal_zgui_win32_d3d12 segfault on exit

[hazeycode]

segfaults on exit for me:

Segmentation fault at address 0x7ffd108a83f8
...\zig-gamedev\samples\minimal_zgui_win32_d3d12\src\minimal_zgui_win32_d3d12.zig:39:22: 0xd61293 in main (minimal_zgui_win32_d3d12.exe.obj)
    defer gctx.deinit(allocator);

only happens when I use the close button and not esc

Originally posted by @Pyrolistical in #562 (comment)

[Pyrolistical]

might be related, but pressing the button fails to print "Button pressed" in console