What?

Closes #60467

Prevents the Site Title block from saving and rendering values made only of whitespace characters

Why?

The Site Title block was inconsistent with the classic admin behavior - it would allow saving site titles with only spaces, which created empty links on the front end. Empty links are problematic for SEO and accessibility.
This inconsistency created a situation where:

• Classic admin wouldn't save site titles with only spaces
• The Site Title block would save them
• This would render an empty link on the frontend

How?

The solution addresses the issue in two places:

• In the editor component (edit.js): Trim whitespace from the title before saving it
• In the PHP render callback (index.php): Skip rendering if the site title consists only of whitespace

Testing Instructions

• Use a theme that has the Site Title block on one of its templates (e.g., Twenty Twenty-Four > Blog Home template)
• Go to the Site Editor and select the Site Title block
• Clear the title and enter only spaces
• Save the template
• Check the frontend - verify no empty link is rendered
• Check the classic admin (Settings > General) - verify the site title field is empty
• Try to enter only spaces in the classic admin site title field and save
• Verify the site title remains empty in both the classic admin and the Site Editor

Screencast

Before

After