userbug not printing on windows

Example: Adding
```c
uiMenuItemOnClicked(quitItem, NULL, NULL);
```
in line 61:
https://github.com/andlabs/libui/blob/7891cd81c28246f336126aab44996a6045a42b8d/test/menus.c#L60-L61

Output on macOS:
```
$ ./out/test
2018-03-18 13:28:33.625 test[14138:186459] [libui] /Users/niklas/Desktop/DEV-TEST/libui/libui/darwin/menu.m:222:uiMenuItemOnClicked() You have a bug: You can't call uiMenuItemOnClicked() on a Quit item; use uiOnShouldQuit() instead.
Illegal instruction: 4
$
```

Crashes on Windows 10 without any error:
```
$ ./out/test
$
```