fdo#80474: Fix the check whether the window is active on OS X.

Change-Id: I68d7d11a93f5d741f2295ef183b2b607ad6833fc
Reviewed-on: https://gerrit.libreoffice.org/11266
Reviewed-by: Jan Holesovsky <kendy@collabora.com>
Tested-by: Jan Holesovsky <kendy@collabora.com>