Resolves: fdo#80681 widget is not transparent

regression from 12dfca2ea61116665a7abefd43a9a4caa2b8920b
Author: Armin Le Grand <alg@apache.org>
Date:   Mon May 14 15:16:00 2012 +0000
    Resolves: #i119307# added deletion of sw's BmpWindow control...
    ...due to the fact that graphics may be transparent

Change-Id: I7eb2ee8ed53f0ef907a4573a735c71de43b6e8d3
(cherry picked from commit 1caad856de1c1c5b0a8c31d2226416a2db9632cd)
Reviewed-on: https://gerrit.libreoffice.org/9987
Reviewed-by: Andras Timar <andras.timar@collabora.com>
Tested-by: Andras Timar <andras.timar@collabora.com>