During iteration of the optimized code list to process weak slots, we
need to clear the next_code_link in the CodeDataContainer of a dying
code object because the CodeDataContainer can still be alive.

BUG=v8:6792

Change-Id: Iec5f7430a4097cb622de2157bdec2a7d539dbba0
Reviewed-on: https://chromium-review.googlesource.com/751663Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49087}