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

Dumper/XliffFileDumper.php

@@ -176,7 +176,7 @@ private function dumpXliff2(string $defaultLocale, MessageCatalogue $messages, ?
             $metadata = $messages->getMetadata($source, $domain);
 
             // Add notes section
-            if ($this->hasMetadataArrayInfo('notes', $metadata)) {
+            if ($this->hasMetadataArrayInfo('notes', $metadata) && $metadata['notes']) {
                 $notesElement = $dom->createElement('notes');
                 foreach ($metadata['notes'] as $note) {
                     $n = $dom->createElement('note');

Tests/Dumper/XliffFileDumperTest.php

@@ -148,6 +148,24 @@ public function testDumpCatalogueWithXliffExtension()
         );
     }
 
+    public function testEmptyMetadataNotes()
+    {
+        $catalogue = new MessageCatalogue('en_US');
+        $catalogue->add([
+            'empty' => 'notes',
+            'full' => 'notes',
+        ]);
+        $catalogue->setMetadata('empty', ['notes' => []]);
+        $catalogue->setMetadata('full', ['notes' => [['category' => 'file-source', 'priority' => 1, 'content' => 'test/path/to/translation/Example.1.html.twig:27']]]);
+
+        $dumper = new XliffFileDumper();
+
+        $this->assertStringEqualsFile(
+            __DIR__.'/../Fixtures/resources-2.0-empty-notes.xlf',
+            $dumper->formatCatalogue($catalogue, 'messages', ['default_locale' => 'fr_FR', 'xliff_version' => '2.0'])
+        );
+    }
+
     public function testFormatCatalogueXliff2WithSegmentAttributes()
     {
         $catalogue = new MessageCatalogue('en_US');

Tests/Fixtures/resources-2.0-empty-notes.xlf

@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="utf-8"?>
+<xliff xmlns="urn:oasis:names:tc:xliff:document:2.0" version="2.0" srcLang="fr-FR" trgLang="en-US">
+  <file id="messages.en_US">
+    <unit id="Ll7LrI6" name="empty">
+      <segment>
+        <source>empty</source>
+        <target>notes</target>
+      </segment>
+    </unit>
+    <unit id="hU8PAYC" name="full">
+      <notes>
+        <note category="file-source" priority="1">test/path/to/translation/Example.1.html.twig:27</note>
+      </notes>
+      <segment>
+        <source>full</source>
+        <target>notes</target>
+      </segment>
+    </unit>
+  </file>
+</xliff>