An empty list points to itself but syncEvents has the list head only and is
of a different format than the elements. Thus, casting it to a QdEventPtr
gives us garbage.
Segfaults with XTS test case Xlib13/XGrabKeyboard
Introduced in 7af23259d8.
Reported-by: Aaron Plattner <aplattner@nvidia.com>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Chase Douglas <chase.douglas@canonical.com>