Readability score outputs as 0th when post content is empty

[SteveJonesDev]

• [x] I've read and understood the contribution guidelines.
• [x] I've searched for any related issues and avoided creating a duplicate issue.

Please give us a description of what happened.

On a post without any text content the readability level outputs as 0th.

Please describe what you expected to happen and why.

It should output None possibly with a description like it does on the Readability tab.

How can we reproduce this behavior?

1. Install Accessibility Checker Free
2. Scan a post with no content
3. View summary tab

Technical info

• WordPress version: 6.5.2
• Accessibility Checker version: 1.11.0
• If relevant, which editor is affected (or editors):
• [ ] Classic Editor
• [x] Gutenberg
• [ ] Classic Editor plugin
• [ ] Page Builder (please specify):

• Which browser is affected (or browsers):

• [ ] Internet Explorer

• [ ] Edge

• [ ] Chrome

• [ ] Firefox

• [ ] Safari

• [x] Brave

• Relevant plugins in case of a bug: None

• Tested with theme: TwentyTwenty Four