Fix some issues found by coverity scans on Node.js

third_party/WebKit/Source/platform/inspector_protocol/ValueConversions.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ValueConversions_h
 #define ValueConversions_h
 
 #include "platform/inspector_protocol/ErrorSupport.h"
 #include "platform/inspector_protocol/Platform.h"
 #include "platform/inspector_protocol/String16.h"
@@ skipping 94 matching lines @@
             errors->addError("string value expected");
         return result;
     }
 };
 
 template<>
 struct FromValue<Value> {
     static std::unique_ptr<Value> parse(protocol::Value* value, ErrorSupport* errors)
     {
         bool success = !!value;
-        if (!success)
+        if (!success) {
             errors->addError("value expected");
+            return nullptr;
+        }
         return value->clone();
     }
 };
 
 template<>
 struct FromValue<DictionaryValue> {
     static std::unique_ptr<DictionaryValue> parse(protocol::Value* value, ErrorSupport* errors)
     {
         bool success = value && value->type() == protocol::Value::TypeObject;
         if (!success)
@@ skipping 20 matching lines @@
     static std::unique_ptr<protocol::Array<T>> parse(protocol::Value* value, ErrorSupport* errors)
     {
         return protocol::Array<T>::parse(value, errors);
     }
 };
 
 } // namespace platform
 } // namespace blink
 
 #endif // !defined(ValueConversions_h)