Merge branch '6.4' into 7.2

* 6.4:
  Fixes XliffFileDumperTest for 6.4
  [HttpClient] Don't send any default content-type when the body is empty
  [VarExporter] Fix lazy objects with hooked properties
  [Translation] check empty notes
  ntfy-notifier: tfix in description

Author: nicolas-grekas

HttpClientTrait.php

@@ -355,9 +355,11 @@ private static function normalizeBody($body, array &$normalizedHeaders = [])
                 }
             });
 
-            $body = http_build_query($body, '', '&');
+            if ('' === $body = http_build_query($body, '', '&')) {
+                return '';
+            }
 
-            if ('' === $body || !$streams && !str_contains($normalizedHeaders['content-type'][0] ?? '', 'multipart/form-data')) {
+            if (!$streams && !str_contains($normalizedHeaders['content-type'][0] ?? '', 'multipart/form-data')) {
                 if (!str_contains($normalizedHeaders['content-type'][0] ?? '', 'application/x-www-form-urlencoded')) {
                     $normalizedHeaders['content-type'] = ['Content-Type: application/x-www-form-urlencoded'];
                 }