SystemUI: fix qs pulldown on certain themes

Some themes define the peek height as 0, we should respect that and
allow the QS pulldown to still work.

Ticket: CYNGNOS-2756

Change-Id: I0404974a23ef41f4689c38ab86e3f09c4bb150ab
Signed-off-by: Roman Birg <roman@cyngn.com>
(cherry picked from commit 9b2e90cb)