number of references can't be invalid if gof was correctly parsed
from a vp9 packet, but RtpFrameReferenceFinder still better be
protected from the invalid data.
Bug: chromium:1048013
Change-Id: I548f5c87199421b7736409cbcacbec760ad799ae
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/168124
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30444}
a118702566