Resolves: rhbz#1467512 mask not created as 1 bit depth

Change-Id: Ib5bdd594efd41eb881dfc4e2454b72e4739ffd56
Reviewed-on: https://gerrit.libreoffice.org/39693
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>
diff --git a/vcl/headless/svpgdi.cxx b/vcl/headless/svpgdi.cxx
index 033389e..c694fc0 100644
--- a/vcl/headless/svpgdi.cxx
+++ b/vcl/headless/svpgdi.cxx
@@ -1110,7 +1110,7 @@ void SvpSalGraphics::drawMask( const SalTwoRect& rTR,
SalBitmap* SvpSalGraphics::getBitmap( long nX, long nY, long nWidth, long nHeight )
{
    SvpSalBitmap* pBitmap = new SvpSalBitmap();
    pBitmap->Create(Size(nWidth, nHeight), 32, BitmapPalette());
    pBitmap->Create(Size(nWidth, nHeight), GetBitCount(), BitmapPalette());

    cairo_surface_t* target = SvpSalGraphics::createCairoSurface(pBitmap->GetBuffer());
    cairo_t* cr = cairo_create(target);