tiff: don't apply the 8 bps predictor to a 1 bps image.

Change-Id: I112fc7189f8afdd54b96562e1989f9fca1d24d68
Reviewed-on: https://go-review.googlesource.com/11135
Reviewed-by: Benny Siegert <bsiegert@gmail.com>
Reviewed-by: Nigel Tao <nigeltao@golang.org>
1 file changed