Describe the bug

When using the speaker sessions block I noticed this issue. It's trivial to work around and isn't causing any roadblocks for me since it was easy enough to temporarily publish as session to see how the block looks / works. I wanted to report in case this wasn't already noticed by anyone else. I am pretty sure most of the block editor stuff for WordCamp.org is relatively unused.

To reproduce

Steps to reproduce the behavior:

1. Using Twenty Twenty-Three Theme
2. Create a custom Single Item: Speaker Template
3. Add the "Speaker Sessions" block to the template
4. Nothing appears in the editor, you can see the block is there in the outline and modify the settings by selecting it via the outline but there's not visible content in the editor other than the empty "frame" or border.

Expected behavior

I'd expect sample data to be displayed in the block, something like "Post Title" in the Post Title block, eg "This is the Title of the Presentation" and "January 1, 2023 at 10:00am" for the title. Sample data.

If I have at least one session published it looks like this isn't a problem as the data from the published session shows up inside the block.

Screenshots

WordCamp

If this is a problem on a specific WordCamp's site, list the site or page URL here.

https://phoenix.wordcamp.org/2023/wp-admin/site-editor.php?postType=wp_template&sidebar=%2F&postId=twentytwentythree%2F%2Fsingle-wcb_speaker

System (please complete the following information):

• Device: Laptop
• OS: Ubuntu 22.04
• Browser: Firefox
• Version: 110.0