Fix null to parameter WordPress#1 ($string) of type string is depreca…

…ted in wp-includes\formatting.php on line 2789

src/wp-includes/l10n.php

@@ -1064,7 +1064,9 @@ function load_script_textdomain( $handle, $domain = 'default', $path = null ) {
 	if ( ! isset( $wp_scripts->registered[ $handle ] ) ) {
 		return false;
 	}
-
+	if(!is_null($path)) {
+		//removing slashes from null doesn't make sense
+	}
 	$path   = untrailingslashit( $path );
 	$locale = determine_locale();