tdf#157795 set color to black outside of of bitmap bounds

Due to commit 81994cb2b8,
transparent areas are now black instead of white.

Change-Id: I9456bb2603d4968a5d5df0a7bdbff48ce9a8e2f4
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/158355
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
Tested-by: Jenkins
Reviewed-by: Patrick Luby <plubius@neooffice.org>

vcl/source/bitmap/BitmapEx.cxx

@@ -677,7 +677,11 @@ namespace
             if (xRead)
             {
                 const Size aDestinationSizePixel(aDestination.GetSizePixel());
-                const BitmapColor aOutside(BitmapColor(0xff, 0xff, 0xff));
+
+                // tdf#157795 set color to black outside of of bitmap bounds
+                // Due to commit 81994cb2b8b32453a92bcb011830fcb884f22ff3,
+                // transparent areas are now black instead of white.
+                const BitmapColor aOutside(0x0, 0x0, 0x0);
 
                 for(tools::Long y(0); y < aDestinationSizePixel.getHeight(); y++)
                 {