Initialize restoration.type to RESTORATION_NONE for grayscale content

Fixes #89.
8 jobs for master in 2 minutes and 16 seconds (queued for 2 seconds)
Status Name Job ID Coverage
  Build
passed build-debian #5093
debian amd64

00:00:29

passed build-debian-aarch64 #5097
aarch64 debian

00:01:37

passed build-debian-aarch64-clang-5 #5098
aarch64 clang5 debian

00:01:04

passed build-debian-static #5094
debian amd64

00:00:31

passed build-debian-werror #5100
debian

00:01:11

passed build-macos #5099
macos

00:00:25

passed build-win32 #5095
win32

00:00:27

passed build-win64 #5096
win64

00:00:31