Fix use-after-free bug in IO timing code.
Fix use-after-free bug in IO timing code.

Introduced in 326c20220120.

weidezhang/dht,weidezhang/dht,sit/dht,weidezhang/dht,sit/dht,weidezhang/dht,weidezhang/dht,sit/dht,sit/dht,sit/dht