fix gdi resource leak (svx/compressgraphicdialog)

Change-Id: Iea6e481384cee4d7e2ff6787c64d3048ba9c9d65
Reviewed-on: https://gerrit.libreoffice.org/37587
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Julien Nabet <serval2412@yahoo.fr>
diff --git a/svx/source/dialog/compressgraphicdialog.cxx b/svx/source/dialog/compressgraphicdialog.cxx
index a622c0a..fb5c545 100644
--- a/svx/source/dialog/compressgraphicdialog.cxx
+++ b/svx/source/dialog/compressgraphicdialog.cxx
@@ -187,7 +187,7 @@ void CompressGraphicsDialog::Update()
    const LocaleDataWrapper& rLocaleWrapper( Application::GetSettings().GetLocaleDataWrapper() );
    sal_Unicode cSeparator = rLocaleWrapper.getNumDecimalSep()[0];

    VclPtr<VirtualDevice> pDummyVDev = VclPtr<VirtualDevice>::Create();
    ScopedVclPtrInstance<VirtualDevice> pDummyVDev;
    pDummyVDev->EnableOutput( false );
    pDummyVDev->SetMapMode( m_aGraphic.GetPrefMapMode() );