Give a proper message when trying to use an empty config file

[jonakeys]

Hi, I'm new to making commits so all feedback is welcome. Of course I put in my best effort.

This code adds a check for an empty config file, as specified by the issue #1420 . If an empty file is found, the programs prints a message and uses the default config, so the user won't be hindered in doing what he tried to do.

I added a bdd test, but couldn't get it to work properly. The test can't seem to find the new 'empty_file.yaml' config I created. Hopefully someone can help me out here.

Checklist

• I have read the contributing doc.
• I have included a link to the relevant issue number.
• I have checked to ensure there aren't other open pull requests
  for the same issue.
• I have written new tests for these changes, as needed.

[micahellison]

Welcome and thanks for the PR, @jonakeys. I had a slightly different intent for the behavior that I realize I hadn't made clear in the original issue: we still want jrnl to fail if the config can't be parsed, rather than falling back to the default config.

Also, the error message should appear when using a default config that's empty too. I added a test for that situation and fixed the other test so that you can take a test-driven approach to this if you'd like.

[jonakeys]

Thanks for your welcoming words and suggestions! I solved the issues and committed the changes. Had to add a condition to the test, because it would always automatically insert a version number and then the file wouldn't be empty.

[wren]

Looks great. Thank you!