FSE - Template: Template changes are not saved

[gigitux]

Describe the bug

If you save a WooCommerce template and refresh the page, you don't see any changes.

To reproduce

Steps to reproduce the behavior:

Be sure that you have: WordPress 5.9, Gutenberg trunk version, WooCommerce 6.0.0, and WooCommerce Blocks trunk

1. Go to Template Page on Full Site Editor.
2. Click on one of the WooCommerce template like Single Product Page.
3. Add a new block (be sure that you don't add it on the header or footer group).
4. Save.
5. Refresh, and you can check that your changes are missing.

Expected behavior

The changes should be visible

Info

It seems that the system saves a new post in the DB and doesn't update the old one. This bug appears after #5375 merged.

Screenshots

Screen.Capture.on.2021-12-15.at.18-44-07.mp4

Environment

WordPress (please complete the following information):

• Core version: 5.9-beta-3
• Gutenberg version (if installed): trunk
• WooCommerce version: [e.g. 3.5.3]: 6.0.0
• WooCommerce Blocks version: [e.g. 1.3.1]: trunk

[gigitux]

This issue is fixed with #5412