don't pass uno interface implementation directly

Passing the implementation instead of an uno reference may result in
lifetime problems if the passed interface is distroyed while the second
one is still valid
see rhbz#579817 with memcheck

sc/inc/nameuno.hxx

@@ -67,7 +67,7 @@ class ScNamedRangeObj : public ::cppu::WeakImplHelper6<
                         public SfxListener
 {
 private:
-    ScNamedRangesObj*       mpParent;
+    com::sun::star::uno::Reference< com::sun::star::sheet::XNamedRanges > mxParent;
     ScDocShell*             pDocShell;
     String                  aName;
     com::sun::star::uno::Reference< com::sun::star::container::XNamed > mxSheet;
@@ -81,7 +81,7 @@ private:
     SCTAB                   GetTab_Impl();
 
 public:
-                            ScNamedRangeObj(ScNamedRangesObj* pParent, ScDocShell* pDocSh, const String& rNm,
+                            ScNamedRangeObj( com::sun::star::uno::Reference< com::sun::star::sheet::XNamedRanges > xParent, ScDocShell* pDocSh, const String& rNm,
                                     com::sun::star::uno::Reference< com::sun::star::container::XNamed > xSheet = com::sun::star::uno::Reference< com::sun::star::container::XNamed > ());
     virtual                 ~ScNamedRangeObj();
 

sc/source/ui/unoobj/nameuno.cxx

@@ -99,8 +99,8 @@ bool lcl_UserVisibleName(const ScRangeData& rData)
     return !rData.HasType(RT_DATABASE) && !rData.HasType(RT_SHARED);
 }
 
-ScNamedRangeObj::ScNamedRangeObj(ScNamedRangesObj* pParent, ScDocShell* pDocSh, const String& rNm, Reference<container::XNamed> xSheet):
-    mpParent(pParent),
+ScNamedRangeObj::ScNamedRangeObj( Reference< sheet::XNamedRanges > xParent, ScDocShell* pDocSh, const String& rNm, Reference<container::XNamed> xSheet):
+    mxParent(xParent),
     pDocShell( pDocSh ),
     aName( rNm ),
     mxSheet( xSheet )
@@ -215,7 +215,7 @@ void ScNamedRangeObj::Modify_Impl( const String* pNewName, const ScTokenArray* p
     if (pNewRanges->insert(pNew))
     {
         ScDocFunc aFunc(*pDocShell);
-        aFunc.SetNewRangeNames(pNewRanges, mpParent->IsModifyAndBroadcast(), nTab);
+        aFunc.SetNewRangeNames(pNewRanges, dynamic_cast<ScNamedRangesObj*>(mxParent.get())->IsModifyAndBroadcast(), nTab);
 
         aName = aInsName;   //! broadcast?
     }