FSE: "home" template results in WSOD

[Sandstromer]

Description

In a FSE theme when making use of a "home.html" template, results in an empty page.

It looks like Gutenberg is trying to load the "header.php", "content.php", and "footer.php" templates which would previously have been included in a classic theme, or the corresponding fallback WP templates, when attempting to load the FSE "home.html" template.
As these old school templates don't exist in FSE, the result is a WSOD on the frontend.

Step-by-step reproduction instructions

1. using TT1-Blocks theme, rename the "index.html" template to "home.html"
2. view the site frontend and notice the empty blank page

Expected behaviour

The home.html template should be called and displayed as appropriate.

Actual behaviour

The home.html template does not display.

Screenshots or screen recording (optional)

Code snippet (optional)

WordPress information

• WordPress version: 5.7
• Gutenberg version: 10.3.1
• Are all plugins except Gutenberg deactivated? Yes
• Are you using a default theme (e.g. Twenty Twenty-One)? TT1-Blocks

Device information

• Device: Desktop
• Operating system: W10
• Browser: Firefox

[aristath]

Assigning to myself.
Also related to bobbingwide/fizzie#58
This seems to be coming from PR #29026

[aristath]

This PR should fix the issue: #30599 👍