Themes: improve search by trimming search string.

Fix an issue where searching installed themes for an empty string resulted in matching all themes.

Props afercia, desrosj, hesyifei, evalarumbe.
Fixes #39041.

Built from https://develop.svn.wordpress.org/trunk@45557


git-svn-id: http://core.svn.wordpress.org/trunk@45368 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/js/theme.js

@@ -180,6 +180,9 @@ themes.Collection = Backbone.Collection.extend({
 		// Start with a full collection
 		this.reset( themes.data.themes, { silent: true } );
 
+		// Trim the term
+		term = term.trim();
+
 		// Escape the term string for RegExp meta characters
 		term = term.replace( /[-\/\\^$*+?.()|[\]{}]/g, '\\$&' );
 

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.3-alpha-45556';
+$wp_version = '5.3-alpha-45557';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.