If we were unlucky and start wrapper compilation exactly after the
isolate started shutting down, we would not have an isolate info any
more in the isolate and would access a nullptr.
This CL fixes that by just returning an invalid operations barrier token
in that case.

R=ahaas@chromium.org

Bug: v8:11878
Change-Id: I6dcb28a21debb12ba812f705cd5c6387c76eda09
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2982339Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75334}