[Bug] --only-tags option includes files that do not have tags

[aaachen]

If I have a file that does not have any tag yet have the tags property, Obsidian represents the file front matter like follows:

---
up:
- '[[Habits Map]]'
created: 2015-02-20
modified: 2020-05-28
tags: null
---

Running obsidian-export with the --only-tags publish option would include this file, even though it shouldn't