This avoids crashing if an application resets the starting bitrate before adding streams to the call. Bug: webrtc:9586 Change-Id: I8d31aba1f4fee40c67c8930f5a32d17700ccadc3 Reviewed-on: https://webrtc-review.googlesource.com/101680 Reviewed-by: Björn Terelius <terelius@webrtc.org> Commit-Queue: Sebastian Jansson <srte@webrtc.org> Cr-Commit-Position: refs/heads/master@{#24808}