1. Fix typo introduced in prior commit.
2. Guard code so TPH does not attempt to use OffThreadSpace.

Bug: v8:9533
Change-Id: I37eeff6a9c6ec4a7c479161a01345aa82c884e54
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2047046Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Steve Blackburn <steveblackburn@google.com>
Cr-Commit-Position: refs/heads/master@{#66214}