This argument is never used as a reference and the pointer that's bound
to the const reference may be nullptr. This is undefined behavior and
barks under UBSan.
BUG=webrtc:5124
R=stefan@webrtc.org
Review URL: https://codereview.webrtc.org/1642863003 .
Cr-Commit-Position: refs/heads/master@{#11418}