Remove NullObjectReceiveStatistics() in rtp_rtcp module

webrtc/modules/rtp_rtcp/include/rtp_rtcp.h

Index: webrtc/modules/rtp_rtcp/include/rtp_rtcp.h
diff --git a/webrtc/modules/rtp_rtcp/include/rtp_rtcp.h b/webrtc/modules/rtp_rtcp/include/rtp_rtcp.h
index 693a6f8373ea351c8ffc47791bf742dc8f03e4f5..c5a53f7a2afcdc429bd13d079e23cd27696c2518 100644
--- a/webrtc/modules/rtp_rtcp/include/rtp_rtcp.h
+++ b/webrtc/modules/rtp_rtcp/include/rtp_rtcp.h
@@ -55,7 +55,7 @@ class RtpRtcp : public Module {
     // The clock to use to read time. If nullptr then system clock will be used.
     Clock* clock = nullptr;
 
-    ReceiveStatistics* receive_statistics;
+    ReceiveStatistics* receive_statistics = nullptr;
 
     // Transport object that will be called when packets are ready to be sent
     // out on the network.