DCHECK that the red payload type doesn't have invalid values when FEC is enabled.

webrtc/modules/rtp_rtcp/source/rtp_sender_video.cc

Index: webrtc/modules/rtp_rtcp/source/rtp_sender_video.cc
diff --git a/webrtc/modules/rtp_rtcp/source/rtp_sender_video.cc b/webrtc/modules/rtp_rtcp/source/rtp_sender_video.cc
index e10b5b2edab45b98689b1d1fec6346bd1115f3b9..3dab6a4bcb572e734245bc71fd08f1ea3ad53ca7 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_sender_video.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtp_sender_video.cc
@@ -169,6 +169,7 @@ void RTPSenderVideo::SendVideoPacketAsRed(uint8_t* data_buffer,
 void RTPSenderVideo::SetGenericFECStatus(const bool enable,
                                          const uint8_t payloadTypeRED,
                                          const uint8_t payloadTypeFEC) {
+  RTC_DCHECK(!enable || payloadTypeRED > 0);
   rtc::CritScope cs(&crit_);
   fec_enabled_ = enable;
   red_payload_type_ = payloadTypeRED;