Draft: demo: Fix cyclic rumbling when no rumble is present
Splitted of from !32 (closed).
Currently, the device is always unref-ed when the device
disconnects because the device is ref-ed for the sake of
rumbling with the timeout. But then, it always unrefs it even
if there's no rumble so there's a double unref in case the
device doesn't have any rumble.
This isn't working, but I'll look into it once the other MR is finished.
Edited by Vanadiae