Account for empty stack trace with non-empty async chain in V8Initializer.

third_party/WebKit/Source/bindings/core/v8/ScriptCallStack.cpp

 /*
  * Copyright (c) 2008, 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 27 matching lines @@
 #include "platform/v8_inspector/public/V8Debugger.h"
 #include "platform/v8_inspector/public/V8StackTrace.h"
 
 namespace blink {
 
 PassRefPtr<ScriptCallStack> ScriptCallStack::create(v8::Isolate* isolate, v8::Local<v8::StackTrace> stackTrace, size_t maxStackSize)
 {
     V8PerIsolateData* data = V8PerIsolateData::from(isolate);
     if (!data->threadDebugger())
         return nullptr;
-    return adoptRef(new ScriptCallStack(data->threadDebugger()->debugger()->createStackTrace(stackTrace, maxStackSize)));
+    OwnPtr<V8StackTrace> stack = data->threadDebugger()->debugger()->createStackTrace(stackTrace, maxStackSize);
+    return stack ? adoptRef(new ScriptCallStack(std::move(stack))) : nullptr;
 }
 
 PassRefPtr<ScriptCallStack> ScriptCallStack::capture(size_t maxStackSize)
 {
     v8::Isolate* isolate = v8::Isolate::GetCurrent();
     if (!isolate->InContext())
         return nullptr;
     V8PerIsolateData* data = V8PerIsolateData::from(isolate);
     if (!data->threadDebugger())
         return nullptr;
@@ skipping 63 matching lines @@
     value->endDictionary();
     value->endArray();
 }
 
 String ScriptCallStack::toString() const
 {
     return m_stackTrace->toString();
 }
 
 } // namespace blink