Cannot create custom gradients when no gradients are set in theme.json

[ndiego]

Description

If you set coreGradients: false (soon to be defaultGradients: false), customGradients: true, but no specified gradients are set in theme.json, the UI for creating custom gradients is not displayed.

Step-by-step reproduction instructions

1. Install the latest version of Twenty Twenty-Two and make sure you are using Gutenberg 12.0.1.

2. In theme.json remove the gradients and set coreGradients: false and customGradients: true like the following.
   

3. Navigate the Block Editor and add a Cover block. Click on the Color panel, switch to Gradients and see the UI in the screenshot above.

Note: It actually does not appear the customGradients: true really does anything anymore. Toggling on and off seems to have no effect.

Screenshots, screen recording, code snippet

No response

Environment info

WordPress 5.9 Beta 1 and Gutenberg 12.0.1

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes

[ndiego]

This issue is fixed with #36900