Set LoggedIceCandidatePairEvent.transaction_id to default value if missing.
Set LoggedIceCandidatePairEvent.transaction_id to default value if missing.

Bug: webrtc:9972
Change-Id: I559ccb6799b494a9013523d3960a725ea7fd448e
Reviewed-on: https://webrtc-review.googlesource.com/c/114240
Reviewed-by: Björn Terelius <efeae16329b3cb4ac5daf80d4bfda3344c027db3@webrtc.org>
Commit-Queue: Zach Stein <d217dcfaf7ca6751b8212d4ba07cd308222c32d1@webrtc.org>
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#26006}
TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc