Related: fdo#58277 if the SwFrm is not IsValid so are its portions

i.e. they don't necessarily match the SwTxtNode anymore, e.g.
content deleted from node, SwFrm is invalid, old portions
refer to old offsets not new ones yet

Change-Id: I755051cd647aa7bb203a6e1f815193fb6ec39191

sw/source/core/text/txtfrm.cxx

@@ -2512,9 +2512,9 @@ void SwTxtFrm::RecalcAllLines()
 
 void SwTxtFrm::VisitPortions( SwPortionHandler& rPH ) const
 {
-    const SwParaPortion* pPara = GetPara();
+    const SwParaPortion* pPara = IsValid() ? GetPara() : NULL;
 
-    if( pPara )
+    if (pPara)
     {
         if ( IsFollow() )
             rPH.Skip( GetOfst() );