action fails if no python files are modified

[valentijnscholten]

When a PR has only changes in non-python fails, the flake8-your-pr results in a failure because it gets an empty value for new_files_in_branch, or maybe the piped sequence of commands fails.

https://github.com/valentijnscholten/django-DefectDojo/pull/5/checks?check_run_id=1170299683

This leads to the check being marked as failure preventing the PR from being merged.