Remove DCHECK when transport feedback on request can't be produced

Bug: chromium:1507210
Change-Id: I840b91dd7143ce6a0d3c9a17df6c187e01a145f9
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/330320
Reviewed-by: Per Kjellander <perkj@webrtc.org>
Commit-Queue: Per Kjellander <perkj@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#41351}

modules/remote_bitrate_estimator/remote_estimator_proxy.cc

@@ -260,8 +260,11 @@ void RemoteEstimatorProxy::SendFeedbackOnRequest(
       feedback_request.include_timestamps, first_sequence_number,
       sequence_number + 1, /*is_periodic_update=*/false);
 
-  // This is called when a packet has just been added.
-  RTC_DCHECK(feedback_packet != nullptr);
+  // Even though this is called when a packet has just been added,
+  // no feedback may be produced when that new packet is too old.
+  if (feedback_packet == nullptr) {
+    return;
+  }
 
   // Clear up to the first packet that is included in this feedback packet.
   packet_arrival_times_.EraseTo(first_sequence_number);

test/fuzzers/BUILD.gn

@@ -248,6 +248,7 @@ webrtc_fuzzer_test("receive_side_congestion_controller_fuzzer") {
     "../../modules/rtp_rtcp:rtp_rtcp_format",
     "../../system_wrappers",
   ]
+  seed_corpus = "corpora/receive-side-cc"
 }
 
 rtc_library("audio_decoder_fuzzer") {