Fix #134

[apeltzer]

PR checklist

• This comment contains a description of changes (with reason).
• If you've fixed a bug or added code that should be tested, add tests!
  • If you've added a new tool - add to the software_versions process and a regex to scrape_software_versions.py
  • If you've added a new tool - have you followed the pipeline conventions in the [contribution docs](https://github.com/nf-core/smrnaseq/tree/master/.github/CONTRIBUTING.md)
  • If necessary, also make a PR on the nf-core/smrnaseq branch on the nf-core/test-datasets repository.
• Make sure your code lints (nf-core lint .).
• Ensure the test suite passes (nextflow run . -profile test,docker).
• Usage Documentation in docs/usage.md is updated.
• Output Documentation in docs/output.md is updated.
• CHANGELOG.md is updated.
• README.md is updated (including new tool citations and authors/contributors).

This only adds a simple bugfix for cases where a sample is entirely zero for all genes that are left after filtering out for zero expression genes in the matrix. Fixes #134 - tests with a broken case are running 👍🏻

[apeltzer]

Confirmed and tested that this indeed fixes the issue 👍🏻

[jfy133]

Confirmed and tested that this indeed fixes the issue 👍🏻

I'll trust you there ;).