add missing dcheck to ToLocalChecked

src/api.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/api.h"
 
 #include <string.h>  // For memcpy, strlen.
 #ifdef V8_USE_ADDRESS_SANITIZER
 #include <sanitizer/asan_interface.h>
 #endif  // V8_USE_ADDRESS_SANITIZER
@@ skipping 599 matching lines @@
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(v8_isolate);
   return Utils::ToLocal(isolate->eternal_handles()->Get(index));
 }
 
 
 void V8::CheckIsJust(bool is_just) {
   Utils::ApiCheck(is_just, "v8::FromJust", "Maybe value is Nothing.");
 }
 
 
+void V8::ToLocalEmpty() {
+  Utils::ApiCheck(false, "v8::ToLocalChecked", "Empty MaybeLocal.");
+}
+
+
 // --- H a n d l e s ---
 
 
 HandleScope::HandleScope(Isolate* isolate) {
   Initialize(isolate);
 }
 
 
 void HandleScope::Initialize(Isolate* isolate) {
   i::Isolate* internal_isolate = reinterpret_cast<i::Isolate*>(isolate);
@@ skipping 7364 matching lines @@
   Isolate* isolate = reinterpret_cast<Isolate*>(info.GetIsolate());
   Address callback_address =
       reinterpret_cast<Address>(reinterpret_cast<intptr_t>(callback));
   VMState<EXTERNAL> state(isolate);
   ExternalCallbackScope call_scope(isolate, callback_address);
   callback(info);
 }
 
 
 } }  // namespace v8::internal