BackgroundMergeTask::CompleteMergeInForeground contained an incorrect
assumption that some SharedFunctionInfos would have bytecode arrays.

Bug: v8:12808, chromium:1360024
Change-Id: I42ca22fc3a4412aea5e5a433e63c685eaf2af242
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3888198Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Seth Brenith <seth.brenith@microsoft.com>
Cr-Commit-Position: refs/heads/main@{#83133}