Lint: Traceback if file empty

[wxtim]

Reproducible Example

mkdir ~/cylc-src/myflow
cd ~/cylc-src/myflow
touch flow.cylc
cylc lint .

Returns traceback

 File "cylc-flow/cylc/flow/scripts/lint.py", line 1226, in check_cylc_file
    for _line in linter:
                 ^^^^^^

Because there are no lines:

Expected Behaviour

Totally empty Cylc files should probably trigger a style warning?