tdf#170968 avoid unnecessary soft edge reset

This fixes a regression from 85dbb4dc81
(tdf#170095 override soft edge if there are 3D effects) where a shape
might stop showing if the soft edge value is set to zero when it wasn't
set to begin with.

Change-Id: I0a886711cef199e4eb3a89a034732e6ef0b1e4c7
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/200155
Reviewed-by: Jaume Pujantell <jaume.pujantell@collabora.com>
Tested-by: Jenkins

oox/source/drawingml/shape.cxx

@@ -1632,10 +1632,10 @@ Reference< XShape > const & Shape::createAndInsert(
             = get3DProperties().getShape3DAttributes(rGraphicHelper, nFillPhClr);
         bool bHas3DProps = aCamera3DEffects.hasElements() || aLightRig3DEffects.hasElements()
                            || aShape3DEffects.hasElements();
-        if (bHas3DProps)
+        if (bHas3DProps && getEffectProperties().maSoftEdge.moRad.has_value())
         {
             // 3D properties override softeEdge
-            getEffectProperties().maSoftEdge.moRad = 0;
+            getEffectProperties().maSoftEdge.moRad.reset();
         }
 
         // applying properties