Filesystem: in `WP_Filesystem_FTPext::parselisting()`, check for the existence of `$b['islink']` before using it.

Props jesin.
Fixes #27975.

Built from https://develop.svn.wordpress.org/trunk@35476


git-svn-id: http://core.svn.wordpress.org/trunk@35440 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/class-wp-filesystem-ftpext.php

@@ -520,8 +520,9 @@ class WP_Filesystem_FTPext extends WP_Filesystem_Base {
 		}
 
 		// Replace symlinks formatted as "source -> target" with just the source name
-		if ( $b['islink'] )
+		if ( isset( $b['islink'] ) && $b['islink'] ) {
 			$b['name'] = preg_replace( '/(\s*->\s*.*)$/', '', $b['name'] );
+		}
 
 		return $b;
 	}

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.4-beta2-35475';
+$wp_version = '4.4-beta2-35476';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.