Godot suppresses X11 BadWindow errors during some operations because
they can occur with normal usage.
X11 errors are asynchronous. Sometimes, when a BadWindow error is sent,
it is dequeued after the original non-BadWindow-suppressing error
handler has been restored. This results in an error callstack being
shown to the user.
Call `XSync` before restoring the original error handler. This ensures
that any queued BadWindow errors go to the suppressing handler.
Fixes#117814
norepro
3ffec30d51