Formatting: Make the check for empty text in `wp_trim_excerpt()` more resilient.

This addresses a regression in [47808], which caused excerpts to be generated from post content if an empty string is passed, but not for other values considered empty, e.g. `null` or `false`.

Props riaanlom, laxman-prajapati, SergeyBiryukov.
Fixes #51042.
Built from https://develop.svn.wordpress.org/trunk@48817


git-svn-id: http://core.svn.wordpress.org/trunk@48579 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/formatting.php

@@ -3808,7 +3808,7 @@ function human_time_diff( $from, $to = 0 ) {
 function wp_trim_excerpt( $text = '', $post = null ) {
 	$raw_excerpt = $text;
 
-	if ( '' === $text ) {
+	if ( '' === trim( $text ) ) {
 		$post = get_post( $post );
 		$text = get_the_content( '', false, $post );
 

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.6-alpha-48816';
+$wp_version = '5.6-alpha-48817';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.