Filesystem API: Don't add `'.'` to the list of directories which need to be checked/created when extracting a file.

Prevents a PHP warning by `WP_Filesystem_Direct::mkdir()` when installing a language pack which doesn't have subdirectories.

Props tfrommen.
Fixes #36570.
Built from https://develop.svn.wordpress.org/trunk@37421


git-svn-id: http://core.svn.wordpress.org/trunk@37387 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/file.php

@@ -643,10 +643,13 @@ function _unzip_file_ziparchive($file, $to, $needed_dirs = array() ) {
 
 		$uncompressed_size += $info['size'];
 
-		if ( '/' == substr($info['name'], -1) ) // directory
-			$needed_dirs[] = $to . untrailingslashit($info['name']);
-		else
-			$needed_dirs[] = $to . untrailingslashit(dirname($info['name']));
+		if ( '/' === substr( $info['name'], -1 ) ) {
+			// Directory.
+			$needed_dirs[] = $to . untrailingslashit( $info['name'] );
+		} elseif ( '.' !== $dirname = dirname( $info['name'] ) ) {
+			// Path to a file.
+			$needed_dirs[] = $to . untrailingslashit( $dirname );
+		}
 	}
 
 	/*

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.6-alpha-37419';
+$wp_version = '4.6-alpha-37421';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.