[debugger] fix crash in debug-evaluate when retrieving values in TDZ.

src/debug/debug-evaluate.cc

 // Copyright 2015 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/debug/debug-evaluate.h"
 
 #include "src/accessors.h"
 #include "src/contexts.h"
 #include "src/debug/debug.h"
 #include "src/debug/debug-frames.h"
@@ skipping 328 matching lines @@
   for (const Handle<String>& name : non_locals_) {
     HandleScope scope(isolate_);
     Handle<Object> value;
     bool global;
     if (!LoadFromContext(context, name, &global).ToHandle(&value) || global) {
       // If resolving the variable fails, skip it. If it resolves to a global
       // variable, skip it as well since it's not read-only and can be resolved
       // within debug-evaluate.
       continue;
     }
+    if (value->IsTheHole()) continue;  // Value is not initialized yet (in TDZ).
     JSObject::SetOwnPropertyIgnoreAttributes(target, name, value, NONE).Check();
   }
 }
 
 
 void DebugEvaluate::ContextBuilder::StoreToContext(Handle<Context> context,
                                                    Handle<String> name,
                                                    Handle<Object> value) {
   static const ContextLookupFlags flags = FOLLOW_CONTEXT_CHAIN;
   int index;
@@ skipping 38 matching lines @@
     LoadFromContext(lookup_context, this_string, &global).ToHandle(&receiver);
   } else if (local_function->shared()->scope_info()->HasReceiver()) {
     receiver = handle(frame_->receiver(), isolate_);
   }
   return isolate_->factory()->NewCatchContext(global_function, parent_context,
                                               this_string, receiver);
 }
 
 }  // namespace internal
 }  // namespace v8