Added IsProperty() check to result in DefineOrRedefineAccessor - if no check ...

src/runtime.cc

Index: src/runtime.cc
===================================================================
--- src/runtime.cc	(revision 3786)
+++ src/runtime.cc	(working copy)
@@ -2906,10 +2906,11 @@
   // If an existing property is either FIELD, NORMAL or CONSTANT_FUNCTION
   // delete it to avoid running into trouble in DefineAccessor, which
   // handles this incorrectly if the property is readonly (does nothing)
-  if (result.type() == FIELD || result.type() == NORMAL
-      || result.type() == CONSTANT_FUNCTION)
+  if (result.IsValid() &&
+      (result.type() == FIELD || result.type() == NORMAL
+       || result.type() == CONSTANT_FUNCTION)) {
     obj->DeleteProperty(name, JSObject::NORMAL_DELETION);
-
+  }
   return obj->DefineAccessor(name, flag_setter->value() == 0, fun, attr);
 }