Don't crash if STUN error message is missing ERROR-CODE attribute.

webrtc/p2p/base/stunport.cc

 /*
  *  Copyright 2004 The WebRTC 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 in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 48 matching lines @@
     if (WithinLifetime(rtc::TimeMillis())) {
       port_->requests_.SendDelayed(
           new StunBindingRequest(port_, server_addr_, start_time_),
           port_->stun_keepalive_delay());
     }
   }
 
   virtual void OnErrorResponse(StunMessage* response) override {
     const StunErrorCodeAttribute* attr = response->GetErrorCode();
     if (!attr) {
-      LOG(LS_ERROR) << "Bad allocate response error code";
+      LOG(LS_ERROR) << "Missing binding response error code.";
     } else {
       LOG(LS_ERROR) << "Binding error response:"
                     << " class=" << attr->eclass()
                     << " number=" << attr->number() << " reason='"
                     << attr->reason() << "'";
     }
 
     port_->OnStunBindingOrResolveRequestFailed(server_addr_);
 
     int64_t now = rtc::TimeMillis();
@@ skipping 430 matching lines @@
   const std::vector<Candidate>& existing_candidates = Candidates();
   std::vector<Candidate>::const_iterator it = existing_candidates.begin();
   for (; it != existing_candidates.end(); ++it) {
     if (it->address() == addr)
       return true;
   }
   return false;
 }
 
 }  // namespace cricket