[18.09 backport] fix panic on empty dockerfile - #199

[18.09 backport] fix panic on empty dockerfile#199

andrewhsu merged 4 commits into

docker-archive:18.09docker-archive/engine:18.09from

thaJeztah:18.09_backport_fix_panic_on_empty_dockerfilethaJeztah/docker:18.09_backport_fix_panic_on_empty_dockerfileCopy head branch name to clipboard