tiff: reject 0-size images

Refuse to encode or decode images where the width or height is 0.
It's not clear that this is ever valid, and mostly exists as a
way to cause surprising behavior when w*h == 0 but w+h is large.

Fixes #78773

Change-Id: I6184e9eb60fdf732a2e81d4fc6bb426b6a6a6964
Reviewed-on: https://go-review.googlesource.com/c/image/+/767401
Reviewed-by: Nicholas Husin <husin@google.com>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Nicholas Husin <nsh@golang.org>