Show a "No themes found" message if the search for an installed theme doesn't produce any results.

props gauravmittal1995 for initial patch.
fixes #28587.
Built from https://develop.svn.wordpress.org/trunk@28890


git-svn-id: http://core.svn.wordpress.org/trunk@28689 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/js/theme.js

@@ -190,6 +190,12 @@ themes.Collection = Backbone.Collection.extend({
 			return match.test( haystack );
 		});
 
+		if ( results.length === 0 ) {
+			this.trigger( 'query:empty' );
+		} else {
+			$( 'body' ).removeClass( 'no-results' );
+		}
+
 		this.reset( results );
 	},
 

wp-admin/themes.php

@@ -233,6 +233,8 @@ foreach ( $themes as $theme ) :
 </div>
 <div class="theme-overlay"></div>
 
+<p class="no-themes"><?php _e( 'No themes found. Try a different search.' ); ?></p>
+
 <?php
 // List broken themes, if any.
 if ( ! is_multisite() && current_user_can('edit_themes') && $broken_themes = wp_get_themes( array( 'errors' => true ) ) ) {