audiotest: Initize pointers to NULL to fix ASAN check.

BUG=chromium:294448
TEST=the error in the bug's page is gone.

Change-Id: Ieafa44df8e91df9a2e6a7c25b2a8fca862d0b4d1
Reviewed-on: https://chromium-review.googlesource.com/169932
Reviewed-by: Hsinyu Chao <hychao@chromium.org>
Tested-by: Yunlian Jiang <yunlian@chromium.org>
Commit-Queue: Yunlian Jiang <yunlian@chromium.org>
1 file changed