R Error: "attempt to use zero-length variable name" when using "Preview on save"

Question

It seems there is a problem on "Preview on Save" option in RStudio 2022.07.1 Build 554.

The code below is saved as "tmp1.Rmd". I can run chunks, and I CAN use Preview button (it works). But I can NOT save with "Preview on Save" option set.
When I change YAML Header output from output: html_notebook to output: html_document the error stops (I saw in this question).
Is this an RStudio bug?
The code:

---
title: "R Notebook"
output: html_notebook
---

# VE

```{r}
x=3  
```  

end