layers: Fix mishandling of VI vs VS validation (Gitlab#69)

This wasn't quite correct. We'd end up trying to run it_a off beyond attribs.end(),
which is invalid and upsets the MS debug stdlib. This is most likely the root cause
of the weirdness that caused people to add _at_end, _first, etc to this function long ago,
so that can all disappear -- but for now, let's just deal with the actual bug.

Signed-off-by: Chris Forbes <chrisforbes@google.com>
2 files changed