The first element of a given iterable argument can be a hole. Thus,
normalize the first element so that we can correctly format the
exception message with "undefined" for a hole element, instead of "NaN".

Bug: v8:7715
Change-Id: I62edd09e361ebeebab642bb82db29b73a2c7b193
Reviewed-on: https://chromium-review.googlesource.com/1038951Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52917}