Coding Standards: Simplify a conditional in get_url_in_content().

As there's an `is_string()` check already, `! empty( $href )` can be simplified to a string comparison, as the other variable types that are checked in `empty()` won't appear.

`empty()` also returns `false` for the string `"0"` which would however be a valid (relative) URL and thus should be detectable by the function.

Follow-up to [60665].

Props TobiasBg.
Fixes #63694.

git-svn-id: https://develop.svn.wordpress.org/trunk@60726 602fd350-edb4-49c9-b593-d223f7449a82

Author: SergeyBiryukov

src/wp-includes/formatting.php

@@ -5989,7 +5989,7 @@ function get_url_in_content( $content ) {
 	$processor = new WP_HTML_Tag_Processor( $content );
 	while ( $processor->next_tag( 'A' ) ) {
 		$href = $processor->get_attribute( 'href' );
-		if ( is_string( $href ) && ! empty( $href ) ) {
+		if ( is_string( $href ) && '' !== $href ) {
 			return sanitize_url( $href );
 		}
 	}