libxkbcommon/test/data/keymaps/empty-symbol-decl.xkb

xkb_keymap {
    xkb_keycodes  { include "evdev+aliases(qwerty)" };
    xkb_types     { include "complete" };
    xkb_compat    { include "complete" };
    xkb_symbols "sym" {
        // This syntax caused the crash in parser before, and is not accepted
        // anymore.
        key <SPC> { , [Space] };
    };
};