fdo#62965: fix crash in Edit Contour dialog

The pObjList is 0, so use pObj's GetModel() which should be the same.
(regression from 115054fe)

Change-Id: Ib20e1806518f7b3b33d3fb4472d79d531ea9f1de

svx/source/svdraw/svdundo.cxx

@@ -738,7 +738,7 @@ SdrUndoObjList::SdrUndoObjList(SdrObject& rNewObj, bool bOrdNumDirect)
         nOrdNum=pObj->GetOrdNum();
     }
 
-    m_pListener = new ObjListListener(*this, *pObj, *pObjList->GetModel());
+    m_pListener = new ObjListListener(*this, *pObj, *pObj->GetModel());
 }
 
 SdrUndoObjList::~SdrUndoObjList()