.. if the original shape fill is defined with a theme

Override the alpha value with the current value get from
FillTransparence API attirbute even if the color is defined
with a style or a color scheme.

Change-Id: I09d26238a9c2b501279e6749687dc535e614bbd6
Reviewed-on: https://gerrit.libreoffice.org/72596
Tested-by: Jenkins
Reviewed-by: Tamás Zolnai <tamas.zolnai@collabora.com>