[Template Editor] Unable to clear out template name to rename it

[annezazu]

Description

If you try to rename a template by fully removing the template name in order to add a new one, a filler name is added in and you're unable to remove the contents/rename properly. This makes renaming very difficult.

Step-by-step reproduction instructions

1. Use a theme with template editor support.
2. Create a new template.
3. Using the top toolbar, try to rename the template by deleting the current contents. See error.

Expected behaviour

Can clear out the template name

Actual behaviour

Upon clearing out the template name, a slug is automatically added in its place.

Screenshots or screen recording (optional)

renaming.templates.mov

WordPress information

• WordPress version: 5.8RC3
• Gutenberg version: 11.0.0
• 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: MacOS
• Browser: Chrome 89

[annezazu]

This still happens in 5.9.

[annezazu]

This still happens in 6.0.