Errors in the callback were not correctly unlocking the mutex, oops.

Bug: v8:12547
Change-Id: If44ebc023b8192605c9f29bfd4099a197110f5c4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3760986
Commit-Queue: Shu-yu Guo <syg@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81708}