Avoid PHP warnings when javascript is output prior to locale initialisation.

This can happen when `wp_die()` is called during the bootstrap process of WordPress, notably, as part of the customizer previewer.

Author: dd32

o2.php

@@ -942,6 +942,10 @@ public function remove_cached_incompatible_oembed( $html, $url, $args ) {
 	 * @return string|array     - The translations object.
 	 */
 	function get_i18n_moment( $locale, $json_encode = true ) {
+		if ( ! $locale ) {
+			$locale = new WP_Locale;
+		}
+
 		$moment = array(
 			'months'         => array_values( $locale->month ),
 			'monthsShort'    => array_values( $locale->month_abbrev ),