Using GetAudio events from SSRCs without incoming packets doesn't make sense, and should be prevented. Bug: b/116685514 Change-Id: I48e38bb780549c71cb5f68d370a6819634ad487d Reviewed-on: https://webrtc-review.googlesource.com/c/114321 Commit-Queue: Ivo Creusen <ivoc@webrtc.org> Reviewed-by: Jakob Ivarsson <jakobi@webrtc.org> Cr-Commit-Position: refs/heads/master@{#26017}