Gutenberg: Latest post: Category selection triggers notice, displayed on front end

[bph]

Describe the bug
"Notice: Undefined index: items in /app/public/wp-includes/rest-api.php on line 1245

To reproduce
Steps to reproduce the behavior:

1. Add Latest Post Block to a page
2. Select Category "Uncategorized"
3. Publish page
4. View page.

Expected behavior
No display of notices.

Screenshots

Tested it with clean install

Desktop (please complete the following information):

• OS: [e.g. iOS] MacOS 10.15.3
• Browser [e.g. chrome, safari] Chrome
• Version [e.g. 22] Version 80.0.3987.163

Additional context
WordPress 5.4 - Note: I was not able to reproduce in 5.4 RC. if that helps with locating things.
Gutenberg 7.8.1

[draganescu]

I was not able to reproduce this with WordPress 5.4 and Gutenberg 7.8.1 even after enabling display all errors in PHP. I wonder if I am missing anything?

[bph]

When trying to edit the page with the Latest Post block, I also get for a brief moment these warnings, before the editor is fully loaded.

[bph]

@draganescu Thanks for testing this. Here is my Block Settings in the sidebar

[bph]

Using the Site Health Troubleshooting Mode on a live site:
It occurs only when Gutenberg plugin is enabled (7.8.1)
There is a chance it'll be fixed with this PR #21359

[draganescu]

@bph I can confirm this now and it is indeed a problem that #21359 may fix. If the block is created in pre 7.8.1 Gutenberg and is filtered, then after upgrading this error starts to show up. Will investigate further!

[draganescu]

Closed by #21359