Removed PHP 7 code

Nyholm · Nyholm · commit e12c555e1de8 · 2017-08-14T22:03:34.000+02:00
diff --git a/src/Symfony/Component/Translation/Dumper/XliffFileDumper.php b/src/Symfony/Component/Translation/Dumper/XliffFileDumper.php
@@ -153,7 +153,7 @@ private function dumpXliff2($defaultLocale, MessageCatalogue $messages, $domain,
                 $notesElement = $dom->createElement('notes');
                 foreach ($metadata['notes'] as $note) {
                     $n = $dom->createElement('note');
-                    $n->appendChild($dom->createTextNode($note['content'] ?? ''));
+                    $n->appendChild($dom->createTextNode(isset($note['content']) ? $note['content'] : ''));
                     unset($note['content']);
 
                     foreach ($note as $name => $value) {
