Catch null email addresses in PunycodeHelper (#41011)

Author: laoneo

libraries/src/String/PunycodeHelper.php

@@ -195,6 +195,11 @@ public static function urlToUTF8($uri)
      */
     public static function emailToPunycode($email)
     {
+        if ($email === null) {
+            @trigger_error(sprintf('Passing null value is deprecated in %s and will throw an exception in 6.0.', __METHOD__), E_USER_DEPRECATED);
+            return '';
+        }
+
         $explodedAddress = explode('@', $email);
 
         // Not addressing UTF-8 user names