Fix null-pointer dereference in RTPSenderVideo.

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 5a565dfa99b1b809ff6b21586a756112ced20ebb..2581333b7a24c1e06cea3ccf6289eaf072d6504f 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_sender_video.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtp_sender_video.cc
@@ -235,9 +235,9 @@ int32_t RTPSenderVideo::SendVideo(const RtpVideoCodecTypes videoType,
     return -1;
   }
 
-  rtc::scoped_ptr<RtpPacketizer> packetizer(
-      RtpPacketizer::Create(videoType, _rtpSender.MaxDataPayloadLength(),
-                            &(rtpHdr->codecHeader), frameType));
+  rtc::scoped_ptr<RtpPacketizer> packetizer(RtpPacketizer::Create(
+      videoType, _rtpSender.MaxDataPayloadLength(),
+      rtpHdr ? &(rtpHdr->codecHeader) : nullptr, frameType));
 
   StorageType storage;
   bool fec_enabled;