Allow parsing RTC event logs without a transaction ID.
Allow parsing RTC event logs without a transaction ID.

Bug: webrtc:9972
Change-Id: I01d60671d249adbd55f25c8f49f205b18787cbf4
Reviewed-on: https://webrtc-review.googlesource.com/c/113304
Reviewed-by: Zach Stein <d217dcfaf7ca6751b8212d4ba07cd308222c32d1@webrtc.org>
Commit-Queue: Björn Terelius <efeae16329b3cb4ac5daf80d4bfda3344c027db3@webrtc.org>
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#25914}
ShiftMediaProject/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc