i18n: Prevent a PHP warning when a mu-plugin loads a textdomain.

`determine_locale()` accesses the `$pagenow` global, but this is set after mu-plugins are loaded, so we need to check that it's been set.

Props swissspidy, azaozz.
See #45668.


Built from https://develop.svn.wordpress.org/branches/5.0@44284


git-svn-id: http://core.svn.wordpress.org/branches/5.0@44114 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/l10n.php

@@ -138,7 +138,7 @@ function determine_locale() {
 		$determined_locale = get_user_locale();
 	}
 
-	if ( ! empty( $_GET['wp_lang'] ) && 'wp-login.php' === $GLOBALS['pagenow'] ) {
+	if ( ! empty( $_GET['wp_lang'] ) && ! empty( $GLOBALS['pagenow'] ) && 'wp-login.php' === $GLOBALS['pagenow'] ) {
 		$determined_locale = sanitize_text_field( $_GET['wp_lang'] );
 	}
 

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.0.2-RC1-44259';
+$wp_version = '5.0.2-RC1-44284';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.