The construct std::vector v; &v[0] doesn't go well with
a checked STL, because the element 0 doesn't exists in an
empty vector, and obviously it doesn't know that whether the
pointer gets de-referenced later.

Bug: angleproject:5980
Change-Id: I690c99bd12d74112fe1081ea3134b6ffb11ad23b
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2900226Reviewed-by: Cody Northrop <cnorthrop@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Gert Wollny <gert.wollny@collabora.com>