Avoid a PHP notice in wp_install_language_form() and wp_dropdown_languages() if the language doesn't have a ISO 639-1 code.

props barrykooij.
fixes #31319.
Built from https://develop.svn.wordpress.org/trunk@31447


git-svn-id: http://core.svn.wordpress.org/trunk@31428 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/l10n.php

@@ -896,7 +896,7 @@ function wp_dropdown_languages( $args = array() ) {
 			$languages[] = array(
 				'language'    => $translation['language'],
 				'native_name' => $translation['native_name'],
-				'lang'        => $translation['iso'][1],
+				'lang'        => current( $translation['iso'] ),
 			);
 
 			// Remove installed language from available translations.
@@ -942,7 +942,7 @@ function wp_dropdown_languages( $args = array() ) {
 			$structure[] = sprintf(
 				'<option value="%s" lang="%s"%s>%s</option>',
 				esc_attr( $translation['language'] ),
-				esc_attr( $translation['iso'][1] ),
+				esc_attr( current( $translation['iso'] ) ),
 				selected( $translation['language'], $args['selected'], false ),
 				esc_html( $translation['native_name'] )
 			);