Fix crash in peerconnection_client example code

Use rtc::scoped_refptr to keep object pointers valid

Bug: webrtc:13993
Change-Id: Iffb6bf47e97606bfa3c2e9d8814a56cf509abbd6
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/259940
Reviewed-by: Tomas Gunnarsson <tommi@webrtc.org>
Commit-Queue: Tomas Gunnarsson <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36645}
diff --git a/AUTHORS b/AUTHORS
index d9ec369..3e3ece4 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -116,6 +116,7 @@
 Vladimir Beloborodov <VladimirTechMan@gmail.com>
 Xiaohong Xu <freemine@yeah.net>
 Xiaolei Yu <dreifachstein@gmail.com>
+Xinchao Tian <tianxinchao@360.cn>
 Yaowen Guo <albertguo88@gmail.com>
 Yura Yaroshevich <yura.yaroshevich@gmail.com>
 Yuriy Pavlyshak <yuriy@appear.in>