fix VirtualDevice GDI handle leaks in SvxNumValueSet

Similar to commit e9392c0c86fcf373e00ede92f8ceeee2c7efd233 (fix
VirtualDevice GDI handle leaks across IconView callers, 2026-02-21).

Change-Id: I521f8cd5679172c5e98172939dd7065cfc8afd86
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/199940
Reviewed-by: Andras Timar <andras.timar@collabora.com>
Tested-by: Jenkins CollaboraOffice <jenkinscollaboraoffice@gmail.com>
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/199949
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>

include/svx/numvset.hxx

@@ -51,7 +51,7 @@ class SVX_DLLPUBLIC SvxNumValueSet : public ValueSet
 {
     NumberingPageType mePageType;
     tools::Rectangle       maOrgRect;
-    VclPtr<VirtualDevice> mpVDev;
+    ScopedVclPtr<VirtualDevice> mpVDev;
 
     css::uno::Reference<css::text::XNumberingFormatter> mxFormatter;
     css::lang::Locale maLocale;

svx/source/dialog/svxbmpnumvalueset.cxx

@@ -407,7 +407,7 @@ FactoryFunction SvxNumValueSet::GetUITestFactory() const
 void SvxNumValueSet::init(NumberingPageType eType)
 {
     mePageType = eType;
-    mpVDev = nullptr;
+    mpVDev.disposeAndClear();
 
     SetColCount( 4 );
     SetLineCount( 2 );