Fix crash on multiple feedback messages are received on old transport.

webrtc/modules/congestion_controller/congestion_controller.cc

 /*
  *  Copyright (c) 2012 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 328 matching lines @@
 void CongestionController::AddPacket(uint16_t sequence_number,
                                      size_t length,
                                      const PacedPacketInfo& pacing_info) {
   transport_feedback_adapter_.AddPacket(sequence_number, length, pacing_info);
 }
 
 void CongestionController::OnTransportFeedback(
     const rtcp::TransportFeedback& feedback) {
   RTC_DCHECK(worker_thread_checker_.CalledOnValidThread());
   transport_feedback_adapter_.OnTransportFeedback(feedback);
+  std::vector<PacketFeedback> feedback_vector =
+      transport_feedback_adapter_.GetTransportFeedbackVector();
+  if (feedback_vector.empty())
+    return;
   DelayBasedBwe::Result result;
   {
     rtc::CritScope cs(&bwe_lock_);
-    result = delay_based_bwe_->IncomingPacketFeedbackVector(
-        transport_feedback_adapter_.GetTransportFeedbackVector());
+    result = delay_based_bwe_->IncomingPacketFeedbackVector(feedback_vector);
   }
   if (result.updated)
     bitrate_controller_->OnDelayBasedBweResult(result);
 }
 
 std::vector<PacketFeedback> CongestionController::GetTransportFeedbackVector()
     const {
   RTC_DCHECK(worker_thread_checker_.CalledOnValidThread());
   return transport_feedback_adapter_.GetTransportFeedbackVector();
 }
@@ skipping 51 matching lines @@
 bool CongestionController::IsSendQueueFull() const {
   return pacer_->ExpectedQueueTimeMs() > PacedSender::kMaxQueueLengthMs;
 }
 
 bool CongestionController::IsNetworkDown() const {
   rtc::CritScope cs(&network_state_lock_);
   return network_state_ == kNetworkDown;
 }
 
 }  // namespace webrtc