Return empty handle from GetEventContext for ScriptCollected events

src/debug.cc

 // Copyright 2006-2008 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 2382 matching lines @@
     }
     return scope.Close(v8::Utils::ToLocal(Handle<String>::cast(json)));
   } else {
     return v8::Utils::ToLocal(response_json_);
   }
 }
 
 
 v8::Handle<v8::Context> MessageImpl::GetEventContext() const {
   Handle<Context> context = Debug::debugger_entry()->GetContext();
+  // Top::context() may have been NULL when "script collected" event occured.
+  if (*context == NULL) {
+    ASSERT(event_ == v8::ScriptCollected);
+    return v8::Local<v8::Context>();
+  }
   Handle<Context> global_context(context->global_context());
   return v8::Utils::ToLocal(global_context);
 }
 
 
 v8::Debug::ClientData* MessageImpl::GetClientData() const {
   return client_data_;
 }
 
 
@@ skipping 105 matching lines @@
 
 
 void LockingCommandMessageQueue::Clear() {
   ScopedLock sl(lock_);
   queue_.Clear();
 }
 
 #endif  // ENABLE_DEBUGGER_SUPPORT
 
 } }  // namespace v8::internal