Fixing an uninitialized variable in webrtcsession_unittest.
Fixing an uninitialized variable in webrtcsession_unittest.

Introduced in https://codereview.webrtc.org/1590333004/

TBR=pthatcher@webrtc.org
NOTRY=true

Review URL: https://codereview.webrtc.org/1617653005

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#11345}

TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc