initialize ctx_.aead_state in ScopedEVPAEADCtx constructor.

net/quic/core/crypto/scoped_evp_aead_ctx.cc

 // Copyright 2014 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.
 
 #include "net/quic/core/crypto/scoped_evp_aead_ctx.h"
 
 namespace net {
 
 ScopedEVPAEADCtx::ScopedEVPAEADCtx() {
   ctx_.aead = nullptr;
+  ctx_.aead_state = nullptr;
 }
 
 ScopedEVPAEADCtx::~ScopedEVPAEADCtx() {
   if (ctx_.aead != nullptr) {
     EVP_AEAD_CTX_cleanup(&ctx_);
   }
 }
 
 EVP_AEAD_CTX* ScopedEVPAEADCtx::get() {
   return &ctx_;
 }
 
 }  // namespace net