Template Editor toolbar dropdown broken

[annezazu]

Description

When editing a template via the template editing mode in the post editor, the dropdown in the toolbar appears to be broken.

Step-by-step reproduction instructions

1. Use a block theme or theme supporting template editing mode
2. Head to a post or page
3. Under Templates in sidebar > Edit
4. Try to click the dropdown in the toolbar.

Screenshots, screen recording, code snippet

drop.down.template.editor.mov

Environment info

• WordPress 5.9 beta 3
• No GB
• TT2

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

[glendaviesnz]

It looks like part of the issue here is that if a template has a template file then the drop down is supposed to display the template description:

... but some templates don't have a description:

There seem to be two ways that we could fix this if template.has_theme_file && template.description === '':

1. Just display the template title with no dropdown
2. Display the dropdown with a generic fallback message

Option 1. seems like a good option as there doesn't seem to be any need to show the dropdown if no description, but I haven't worked on this area at all so there may be something I am overlooking.

[Mamaduka]

I think I know the reason for the regression. I will push the fix for the issue shortly.