If there are only buffers with data revision 0, getLatestStorage will skip
over them.  Fixed the if statement so that it will always find a buffer if
one exists.

BUG=angle:644

Change-Id: I24fc426383c9ae18b7ccf2f8937a9daa7a071ebe
Reviewed-on: https://chromium-review.googlesource.com/198826Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>