From 38340f02884e2f11244db4e15ff05c035fe512f1 Mon Sep 17 00:00:00 2001
From: mpv <mikhail.ponikarov@opencascade.com>
Date: Mon, 22 Dec 2014 18:22:16 +0300
Subject: [PATCH] Issue #285 - crash on invalid reference opened in document

---
 src/Model/Model_AttributeReference.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/Model/Model_AttributeReference.cpp b/src/Model/Model_AttributeReference.cpp
index 2b0e15756..43bbabe65 100644
--- a/src/Model/Model_AttributeReference.cpp
+++ b/src/Model/Model_AttributeReference.cpp
@@ -69,7 +69,9 @@ ObjectPtr Model_AttributeReference::value()
           owner()->document());
       if (aDoc) {
         TDF_Label aRefLab = myRef->Get();
-        return aDoc->object(aRefLab);
+        if (!aRefLab.IsNull()) {  // it may happen with old document, issue #285
+          return aDoc->object(aRefLab);
+        }
       }
     }
   }
-- 
2.39.2