Fix assertion failure introduced by my previous change.

src/hydrogen-instructions.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 396 matching lines @@
   HType type = CalculateInferredType();
   bool result = (!type.Equals(type_));
   type_ = type;
   return result;
 }
 
 
 void HValue::RegisterUse(int index, HValue* new_value) {
   HValue* old_value = OperandAt(index);
   if (old_value == new_value) return;
-  if (old_value != NULL) {
-    ASSERT(old_value->uses_.Contains(this));
+  if (old_value != NULL && old_value->uses_.Contains(this)) {
     old_value->uses_.RemoveElement(this);
   }
   if (new_value != NULL) {
     new_value->uses_.Add(this);
   }
 }
 
 
 void HValue::AddNewRange(Range* r) {
   if (!HasRange()) ComputeInitialRange();
@@ skipping 1081 matching lines @@
 
 
 void HCheckPrototypeMaps::Verify() {
   HInstruction::Verify();
   ASSERT(HasNoUses());
 }
 
 #endif
 
 } }  // namespace v8::internal