The previous clear mechanism would also unnecessarily allocate a preparser.

This fixes regressions introduced by
https://chromium-review.googlesource.com/c/v8/v8/+/1238614

Change-Id: Ia3eef371c80857f2cd6cdd5852c849fa7f8716fc
Reviewed-on: https://chromium-review.googlesource.com/1238918
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56171}