### Bug description

In a quarto website/blog project, I put this in `_quarto.yml` to set the "default" author:

```yaml
format:
  html:
    author: someAuthor
```

And I don't want to display it on the main page, so I put `author: Null` in `index.qmd`. This worked well with quarto ported with RStudio 2022.07.1 (seems to be v1.0.36), but after I installed quarto 1.1.163 in my system (Kubuntu 22.04.1), the project refuses to render, saying

```
ERROR: Validation of YAML front matter failed.
ERROR: In file index.qmd
(line 3, columns 9--12) Key author has value Null, which must be an object
2: title: "test"
3: author: Null
           ~~~
4: ---
✖ The value Null is a null value.
ℹ The error happened in location author.
```

I installed the 1.2.15 official pre-release and the problem remains. 

The problem can be minimally reproduced by 

1. Open a new quarto website project in RStudio
2. In `_quarto.yml`, set 
    ```yaml
    format:
      html:
        author: someAuthor
    ```
3. And set `author` to be `Null`, `null` or `~` in `index.qmd`. (BTW I remember having `author: null` renders as if `null` is a string with quarto 1.0.36, unsure though)

I guess it's the YAML validator that blocks the page from rendering. Since it worked fine in the earlier version, I suppose it's valid YAML...

### Checklist

- [X] Please include a minimal, fully reproducible example in a single .qmd file? Please provide the whole file rather than the snippet you believe is causing the issue.
- [X] Please [format your issue](https://yihui.org/issue/#please-format-your-issue-correctly) so it is easier for us to read the bug report.
- [X] Please document the RStudio IDE version you're running (if applicable), by providing the value displayed in the "About RStudio" main menu dialog?
- [X] Please document the operating system you're running. If on Linux, please provide the specific distribution.
cscheid
2022-08-30T13:23:16Z
mksinicus
bug yaml-validation
v1.3
closed
Project-wide YAML metadata cannot be suppressed
https://github.com/quarto-dev/quarto-cli/issues/2210