With stress bytecode flushing it's possible for the main SFI of a script to have it's
bytecode flushed during deserialization of the script. If this happens, just fall-through
to recompile the SFI.

BUG=v8:8901,v8:8395

Change-Id: I786c1ca93167b76810481892ade525d14ff9168f
Reviewed-on: https://chromium-review.googlesource.com/c/1485837Reviewed-by: Mythri Alle <mythria@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59831}