Fix dangling pointer

Change-Id: I352702ac50708a8f8c40e2752821178223052b7c

sw/source/core/doc/doctxm.cxx

@@ -156,6 +156,7 @@ void SwDoc::DeleteTOXMark( const SwTOXMark* pTOXMark )
     SwTxtNode& rTxtNd = const_cast<SwTxtNode&>(pTxtTOXMark->GetTxtNode());
     OSL_ENSURE( rTxtNd.GetpSwpHints(), "cannot be deleted" );
 
+    std::unique_ptr<SwRegHistory> aRHst;
     if (GetIDocumentUndoRedo().DoesUndo())
     {
         // save attributes for Undo
@@ -164,8 +165,8 @@ void SwDoc::DeleteTOXMark( const SwTOXMark* pTOXMark )
             RES_TXTATR_TOXMARK );
         GetIDocumentUndoRedo().AppendUndo( pUndo );
 
-        SwRegHistory aRHst( rTxtNd, &pUndo->GetHistory() );
-        rTxtNd.GetpSwpHints()->Register( &aRHst );
+        aRHst.reset(new SwRegHistory(rTxtNd, &pUndo->GetHistory()));
+        rTxtNd.GetpSwpHints()->Register(aRHst.get());
     }
 
     rTxtNd.DeleteAttribute( const_cast<SwTxtTOXMark*>(pTxtTOXMark) );