Make GetDebugContext a bit more robust.

src/debug.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/api.h"
 #include "src/arguments.h"
 #include "src/bootstrapper.h"
 #include "src/code-stubs.h"
@@ skipping 2786 matching lines @@
   Handle<Object> exec_state;
   // Bail out and don't call debugger if exception.
   if (!MakeExecutionState().ToHandle(&exec_state)) return;
 
   CallEventCallback(event, exec_state, event_data, NULL);
 }
 
 
 Handle<Context> Debug::GetDebugContext() {
   DebugScope debug_scope(this);
+  if (debug_scope.failed()) return Handle<Context>();
   // The global handle may be destroyed soon after.  Return it reboxed.
   return handle(*debug_context(), isolate_);
 }
 
 
 void Debug::NotifyMessageHandler(v8::DebugEvent event,
                                  Handle<JSObject> exec_state,
                                  Handle<JSObject> event_data,
                                  bool auto_continue) {
   // Prevent other interrupts from triggering, for example API callbacks,
@@ skipping 584 matching lines @@
   logger_->DebugEvent("Put", message.text());
 }
 
 
 void LockingCommandMessageQueue::Clear() {
   base::LockGuard<base::Mutex> lock_guard(&mutex_);
   queue_.Clear();
 }
 
 } }  // namespace v8::internal