tdf#138326 impress template thumbnails are blurred

regression from
    commit 548d77d0c06f7088dd3eb408797aa1fc1d7eb277
    Author: Noel <noelgrandin@gmail.com>
    Date:   Fri Nov 13 10:23:36 2020 +0200
    tools::Long->sal_uInt16 in ImpErrorQuad

Change-Id: I29403afcb7d88dee27f1565793ffbd7ad4c53a17
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/106545
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
diff --git a/vcl/inc/bitmap/impoctree.hxx b/vcl/inc/bitmap/impoctree.hxx
index 50083e3..7c464db 100644
--- a/vcl/inc/bitmap/impoctree.hxx
+++ b/vcl/inc/bitmap/impoctree.hxx
@@ -24,9 +24,9 @@

class ImpErrorQuad
{
    sal_uInt16 nRed;
    sal_uInt16 nGreen;
    sal_uInt16 nBlue;
    sal_uInt32 nRed;
    sal_uInt32 nGreen;
    sal_uInt32 nBlue;

public:
    ImpErrorQuad()