Don't be so CRASH happy in the bindings layer.

WebCore/bindings/v8/custom/V8MutationCallbackCustom.cpp

 /*
  * Copyright (C) 2010 Google Inc. 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
@@ skipping 52 matching lines @@
         return true;
 
     v8::Context::Scope scope(v8Context);
 
     v8::Local<v8::Array> mutationsArray = v8::Array::New(mutations->size());
     for (size_t i = 0; i < mutations->size(); ++i)
         mutationsArray->Set(v8::Integer::New(i), toV8(mutations->at(i).get()));
 
     v8::Handle<v8::Value> observerHandle = toV8(observer);
     if (observerHandle.IsEmpty()) {
-        CRASH();
+        if (!isScriptControllerTerminating())
+            CRASH();
         return true;
     }
 
     v8::Handle<v8::Value> argv[] = {
         mutationsArray,
         observerHandle
     };
 
     bool callbackReturnValue = false;
     return !invokeCallback(m_callback, 2, argv, callbackReturnValue, scriptExecutionContext());
 }
 
 } // namespace WebCore
 
 #endif // ENABLE(MUTATION_OBSERVERS)