Broken article with empty content

### Short description

I was trying to save article with empty content.

### Expected behaviour

I expected that there will be an error "Fill the required field" or the article will be saved with empty content correctly.

### Actual behaviour

I saw was that there is now an article with `{"blocks":[]}` content. And also it is impossible to delete it via admin panel.

### Steps to reproduce

1. Create new article
2. Fill required title and short description
3. Tick "Hide from list of articles" (optional)
4. Save

https://codex.so/article/341