tdf#84228: Fix annoying double shadow in preview

SfxItemSet passed to ActivatePage method contains both rectangle AND
shadow attributes, causing the old shadow to stick around even after
new shadow attributes have been set. Thus, set shadow to none in a
local copy of SfxItemSet and use that one to repaint the rectangle

Change-Id: If798351fbecaaf951ef0479ae4a2c70d2db68ca4

cui/source/tabpages/tpshadow.cxx

@@ -222,8 +222,15 @@ void SvxShadowTabPage::ActivatePage( const SfxItemSet& rSet )
                 else
                     m_pLbShadowColor->SelectEntryPos( nPos );
 
+                SfxItemSet rAttribs( rSet );
+                // rSet contains shadow attributes too, but we want
+                // to use it for updating rectangle attributes only,
+                // so set the shadow to none here
+                SdrOnOffItem aItem( makeSdrShadowItem( false ));
+                rAttribs.Put( aItem );
+
+                m_pCtlXRectPreview->SetRectangleAttributes( rAttribs );
                 ModifyShadowHdl_Impl( this );
-                m_pCtlXRectPreview->SetRectangleAttributes(rSet);
             }
             nPageType = PT_SHADOW;
         }