Empty lines are not being ignored and causes a comment to be interpreted as a parser directive

[rcjsuen]

 
#escape=a
FROM alpine

According to the specification, parser directives must be at the top of the Dockerfile. However, the above Dockerfile will have its second line parsed as a parser directive and a warning will be generated about the a not being a backtick or a backslash. However, since it is on the second line and not actually at the top of the Dockerfile, it should be considered as a comment and not a parser directive and no validation diagnostics should be generated.