Instead of checking for the null TNode, we can use base::Optional.

Bug: v8:6949
Change-Id: I550b2fdb507c61ea6128a0631351b22a8542d4d3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2737296
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Reviewed-by: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73260}