Fix deprecation warning on AMP validation post edit screen

[thelovekesh]

Summary

On a post-edit screen, the title is determined using the edit_item label in the post object and post title which returns a string for the title like Edit post "Post title".

In our case, edit_item is being set as an empty string which causes a deprecation warning with the PHP 8.1+ version.

Since we want to stop the passing null deprecation warning, this PR is a space in the string('' -> ' ') that stops the warning.

Checklist

• My code is tested and passes existing tests.
• My code follows the Engineering Guidelines (updates are often made to the guidelines, check it out periodically).

[github-actions]

Plugin builds for 68745e4 are ready 🛎️!

• Download development build
• Download production build

Checksums

# Development build checksums
f90a66829c58b0cfd1e853deb0c0d9f49ab0882c17c0f2b39d3a46fff44262d1 *amp.zip

# Production build checksums
76411b709620f2732f3ab3f2e1353343e8658c50488ed5dba5a50446c889c64f *amp.zip

Warning

These builds are for testing purposes only and should not be used in production.

[westonruter]

Interesting, as '' is an empty string and not null, right?

[westonruter]

And passing '' as the 3rd arg to preg_replace() doesn't cause a deprecation warning: https://3v4l.org/IerE4

Although passing null does: https://3v4l.org/vFJJS

[westonruter]

In short, I don't see how the change should fix the issue.

[thelovekesh]

It short-circuits the logic to determine the title when the title is empty.

https://github.com/WordPress/wordpress-develop/blob/126d780de939cb4036e53cd8abe705426767661c/src/wp-admin/includes/plugin.php#L1976

We are already filtering title so a fallback isn't required anyway

amp-wp/includes/validation/class-amp-validated-url-post-type.php

Line 3093 in 68745e4

public static function filter_admin_title( $admin_title ) {

[pavanpatil1]

QA Passed ✅

Cross-checked the issue and it is working fine. The deprecation warning is not visible now.

Before fix	After fix